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Positional PER

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Post#1 Positional PER
Tue Jan 1, 2013 7:33 pm by Alfred

PER at each position is radically different. It's much higher at the PG and PF positions, and much lower at the wing positions.

Because positional crossover isn't common, shouldn't we be comparing players to other players at their positions? For example, which has higher value, a 17 PER player at the PG position, or a 15 PER player at the 3? The comparative production of the SF might outstrip that of the PG.

Is there a way of quantifying this discrepancy?
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Post#2 Re: Positional PER
Wed Jan 2, 2013 12:39 pm by turk3d

I think you make a great point and this is something I've been thinking about. Wouldn't it be better to statistically compare teams (as well as players) by position? You could even do a +/- by position which would tell you where your teams weaknesses (and strengths) are, as well as look at individual players and how they stack up against the opposition. Maybe this exists already but I think it would be quite useful. It actually could simplify things a little.
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Post#3 Re: Positional PER
Fri Jan 4, 2013 9:11 am by branny

turk3d wrote:I think you make a great point and this is something I've been thinking about. Wouldn't it be better to statistically compare teams (as well as players) by position? You could even do a +/- by position which would tell you where your teams weaknesses (and strengths) are, as well as look at individual players and how they stack up against the opposition. Maybe this exists already but I think it would be quite useful. It actually could simplify things a little.


Would be quite useful/interesting to look at!
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Post#4 Re: Positional PER
Fri Jan 4, 2013 7:28 pm by Doctor MJ

Alfred wrote:PER at each position is radically different. It's much higher at the PG and PF positions, and much lower at the wing positions.

Because positional crossover isn't common, shouldn't we be comparing players to other players at their positions? For example, which has higher value, a 17 PER player at the PG position, or a 15 PER player at the 3? The comparative production of the SF might outstrip that of the PG.

Is there a way of quantifying this discrepancy?


Wait, it's much HIGHER at the PG? Please elaborate on this. Traditionally top point guards are the most underrated players by this metric.

To your general idea, I'd put this in terms of an "uncanny valley" of sorts. You're quite write that different types of players get over & underrated by the raw PER metric, so further adjustments make sense. However, just splitting it up by position doesn't help that much because "position" according to the NBA is one of only 5 roles despite the fact that there are vastly more roles than that, and PER manages to over & underrate within the same position.
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Post#5 Re: Positional PER
Sat Jan 5, 2013 4:27 pm by turk3d

There is a difficulty due to the way the NBA is run these days (positions seem to float all over the place). However, to simplify things there are always only 5 players on the floor (hence 5 positions for want of a better term, feel free to change it to another name. What we are accustomed to is 1-PG, 2-SG, 3-SF, 4-PF and 5-C. Regardless of how it stacks up, Each of the 5 players on each team has to match up (play defense) on 1 of the 5 players on the opposing team.

If you measured the +/- impact on each of these matchups, you'd get a pretty clear picture of who's doing their job. I feel that most of these metrics (even the +/- 5 player units) is a bit unfair because they basically don't tell you what's really important imo how a guy stacks up against the player (or players) he's actually matched up against, he's subject to what the rest of his teammates do.

Now I realize that the justification for doing it this way is that is that it's about how a guy makes his teammates "better" or "worse". But my answer to that is what happens if the same player is afforded the same opportunity to play with the same unit (for the same number of minutes to get an equal sample size)? Just because the +/- may be + for certain unit doesn't mean it would be even better (more +) if another player were afforded the same opportunity.

Typically what happens if it's positive it may bet stuck with, however an individual player on that unit may be getting beat out on whoever it is that he's individually matched up with and might be carried by the rest of his teammates giving what appears to be a positive result. This does not mean that the team wouldn't perform even better with another player in that same position.

To me the only way to compare players fairly is to look at them individually (before looking collectively). If your 5 players outscore the oppositions 5 players (which you would see if you looked at each position individually 1-5) I don't care by how many points, you win every time.
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Post#6 Re: Positional PER
Tue Jan 8, 2013 3:19 pm by Alfred

Doctor MJ wrote:
Alfred wrote:PER at each position is radically different. It's much higher at the PG and PF positions, and much lower at the wing positions.

Because positional crossover isn't common, shouldn't we be comparing players to other players at their positions? For example, which has higher value, a 17 PER player at the PG position, or a 15 PER player at the 3? The comparative production of the SF might outstrip that of the PG.

Is there a way of quantifying this discrepancy?


Wait, it's much HIGHER at the PG? Please elaborate on this. Traditionally top point guards are the most underrated players by this metric.


I used Hoopdata to determine what the average PER is for players playing over 15 minutes a game (why? Thought it would filter out some of the "noise" generated by players who might not have a defined position playing so few minutes. This might be totally incorrect.)

http://www.hoopdata.com/advancedstats.aspx?team=%&type=pg&posi=PG&yr=2013&gp=0&mins=15
http://www.hoopdata.com/advancedstats.aspx?team=%&type=pg&posi=SG&yr=2013&gp=0&mins=15
http://www.hoopdata.com/advancedstats.aspx?team=%&type=pg&posi=SF&yr=2013&gp=0&mins=15
http://www.hoopdata.com/advancedstats.aspx?team=%&type=pg&posi=PF&yr=2013&gp=0&mins=15
http://www.hoopdata.com/advancedstats.aspx?team=%&type=pg&posi=C&yr=2013&gp=0&mins=15

If you check out last year as well, it's similar, with the PERs being higher at PF, PG and C, and much lower at the swing positions.
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Post#7 Re: Positional PER
Tue Jan 8, 2013 3:22 pm by Alfred

You'll have to copy and paste those into your browser if they aren't fully loaded.
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Post#8 Re: Positional PER
Wed Jan 9, 2013 12:14 am by Doctor MJ

Alfred wrote:]
If you check out last year as well, it's similar, with the PERs being higher at PF, PG and C, and much lower at the swing positions.


I like that you're trying to analyze it like this but you said "radically differs".

The point guard number there is well under 1 point different than the small forward number, and if you move the threshold to 25 minutes, the gap becomes less than 0.15. This is not a radical difference. This is the same ballpark, influenced by the players involved in the league at the moment.

In other words, shooting guards come across sucking here because shooting guards in the league happen to suck right now.

Historically for example, Magic never had a season with a PER north of 24.0 until he became the team's first scoring option, which means that PER view the true pass-first version of Magic being roughly equal to Gilbert Arenas. Now, I suppose you could say that Arenas is technically a point guard, but that's really my point. Arenas is, whether he's a shooting guard or a point guard, was certainly not getting underrated by the stat, but the true point guard get horribly jobbed.

Getting back to the bigs, I think you've got a stronger case there. The gaps I see on Hoopdata are bigger there. I don't know if that's necessarily wrong though. Even ignoring the whole sample size of the moment issue, wingmen have had no problem putting up GOAT level numbers in the stat. Do you look at PER and think that the greats at these positions are terribly off the mark? If they seem okay, then is this truly a bias?
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Post#9 Re: Positional PER
Wed Jan 9, 2013 11:24 am by Alfred

In other words, shooting guards come across sucking here because shooting guards in the league happen to suck right now.


You're missing the point. I don't care about the historical. I care about the present. How good is a shooting guard right now compared to other shooting guards in the league? If a SG has a PER of 15, and every other SG in the league has a PER of 10, then that player is going to be worth more than a PF with a PER of 15 in a league where an average PF has a PER of 20.

Also, a league-wide PER difference of ~4 between bigs and swings IS massive. The sample size is also pretty big too (this season and last).
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Post#10 Re: Positional PER
Wed Jan 9, 2013 4:43 pm by mysticbb

Alfred wrote:If a SG has a PER of 15, and every other SG in the league has a PER of 10, then that player is going to be worth more than a PF with a PER of 15 in a league where an average PF has a PER of 20.


Why should that be the case, if the overall game concept consists of having 5 players on one side against 5 players on the other side? Basketball is not a game of 5 individual 1on1 games, but one 5on5 game, in which each team tries to outscore the opponents in order to win the game. How much a player contributes to the win is NOT determined by how much his PER is higher than the PER of the player who is supposed to play the "same" position on the other team.

If PER is a useful representation of the player's impact on the outcome of the game, no positional adjustment is needed at all. If it is not, no positional adjustment whatsoever will change that.

Alfred wrote:Also, a league-wide PER difference of ~4 between bigs and swings IS massive. The sample size is also pretty big too (this season and last).


The difference is much smaller due to the fact that hoopdata incorrectly is giving out the simple average instead of the minute weighted average. The difference between bigs (PF+C ~ 15.85 PER) and wings (SG+SF ~ 14.09 PER) is 1.76 or 12.5%. That is hardly massive at all. One of the reasons: not so skilled bigs are getting replaced by more skilled wings players, reducing the amount of minutes low PER bigs are getting in order to give more minutes to skilled wing players (players like James, Durant, Anthony, etc. getting minutes at PF for example). Right now the wings have 10000 minutes more playing time than the bigs. If that would be shifted back to the lower PER bigs as it was before, the bigs minute weighted PER would drop again. At the same time lower PER wing players are getting more minutes, which is decreasing the average for those wings. But the point of the game, as I mentioned before, is to win as a team anyway.

Historically, PER has no specific bias towards any position, just a bias towards scoring and against defense, if a player does not create boxscore entries.
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Post#11 Re: Positional PER
Wed Jan 9, 2013 8:13 pm by turk3d

Why should that be the case, if the overall game concept consists of having 5 players on one side against 5 players on the other side? Basketball is not a game of 5 individual 1on1 games, but one 5on5 game, in which each team tries to outscore the opponents in order to win the game.

True, but the fact remains that if you were to take total points scored at each position for each time and added them up, you'd get the same result. Hence, this becomes a simplified way to find out where the pluses are coming from, as well as the minuses and allow you to attempt to make the appropriate adjustments, by making substitutions in order to improve that outcome (it's just a slightly different way to quantify things).

And also, I agree who cares about the past? What's important is the present and what's going to improve your present situation. Past data sure has it's uses, but during the season you're more concerned about improving the present. One of the problems is that the past doesn't take into account (especially the more years a years a player has behind him) is if/when a guy might be having a breakout year (or for that matter a downer year). I think there could be value in doing it both ways.
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Post#12 Re: Positional PER
Wed Jan 9, 2013 9:20 pm by Alfred

mysticbb wrote:
Alfred wrote:If a SG has a PER of 15, and every other SG in the league has a PER of 10, then that player is going to be worth more than a PF with a PER of 15 in a league where an average PF has a PER of 20.


Why should that be the case, if the overall game concept consists of having 5 players on one side against 5 players on the other side?


Because generally, one PG, one SG, one SF, one PF and one C are on the court at the same time. That isn't always the case, but positions do matter.

Who you are replacing a player with is just as important as how good that player is. If their competition is terrible, then they become more valuable. It's like in baseball -- a catcher hitting a so-so average is decidedly more important than a first baseman hitting a so-so average.

Alfred wrote:Also, a league-wide PER difference of ~4 between bigs and swings IS massive. The sample size is also pretty big too (this season and last).


The difference is much smaller due to the fact that hoopdata incorrectly is giving out the simple average instead of the minute weighted average. The difference between bigs (PF+C ~ 15.85 PER) and wings (SG+SF ~ 14.09 PER) is 1.76 or 12.5%. That is hardly massive at all. One of the reasons: not so skilled bigs are getting replaced by more skilled wings players, reducing the amount of minutes low PER bigs are getting in order to give more minutes to skilled wing players (players like James, Durant, Anthony, etc. getting minutes at PF for example). Right now the wings have 10000 minutes more playing time than the bigs. If that would be shifted back to the lower PER bigs as it was before, the bigs minute weighted PER would drop again. At the same time lower PER wing players are getting more minutes, which is decreasing the average for those wings. But the point of the game, as I mentioned before, is to win as a team anyway.


I don't really see why we should care about the weighted minutes? The value of the proposed stat is that it allows you to gauge a player based on the strength of his peers at his position. If he is producing at a level that outstrips his competition at that position, his value is higher than someone who doesn't.
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Post#13 Re: Positional PER
Thu Jan 10, 2013 12:35 am by Doctor MJ

Alfred wrote:
In other words, shooting guards come across sucking here because shooting guards in the league happen to suck right now.


You're missing the point. I don't care about the historical. I care about the present. How good is a shooting guard right now compared to other shooting guards in the league? If a SG has a PER of 15, and every other SG in the league has a PER of 10, then that player is going to be worth more than a PF with a PER of 15 in a league where an average PF has a PER of 20.


Granting that if the variance is big enough that could be an issue, to me the big thing I'm seeing from what you're saying that leaves me saying "Whoa hold on!" is the idea that the average shooting guard is by definition as valuable as the average big, and by extension that the average shooting guard in any one year must be by definition as valuable as the average shooting guard in any other year.

mystic's saying good things relating to this but in my own words:

If the quality of 2's in the league goes down, more responsibility gets shifted to other positions. Yes to an extent the fact that there is an average size associated with 2's means that there is a replaceability aspect of the 2 that cannot be taken up by another position which limits how far the value of the average 2 can fall, but it certainly does not mean that it cannot fall at all.

Of course there is a question of how big that fall is relative to the typical average value of the position. If you believe that fall can't possibly be major, then you'd certainly want a stat that judges the positions separately.

This seems rather absurd to me. Let's consider the career of Derek Fisher. The dude gets way too much hate because he plays a role that most teams don't really have: secondary guard, smallest defender. People judge him compared to point guards because that's his official position, but that's not his job. His job is to fill in the gaps, just like pretty much any other role player. It is something to be values...

this does not make him as valuable as Kobe Bryant though. And if every team in the league decided to run offenses that let their 2 be the lead guard, then this would change the 1's in secondary guards who were not as valuable.

Now, teams haven't decided they no longer want people of 2 size to be their lead guard. That isn't way 2's have dropped. It isn't quite THAT dramatic. However, the fact remains that talent can ebb and flow, and that to the extent PER is measuring everything we want to measure (it isn't of course but that's another thread) there SHOULD be some some drop when the talent drops.
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Post#14 Re: Positional PER
Thu Jan 10, 2013 12:40 am by Doctor MJ

I guess more succinctly, we're running into a bit of a recent pet peeve of mind. I see threads saying, "Is OJ Mayo a top 5 shooting guard?", and it makes think "Why would anyone care?". Even if he is Top 5 at his position, if he's a volume scorer who can't volume score super-effectively, I'm not going to pay him like he's an elite player.
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Post#15 Re: Positional PER
Thu Jan 10, 2013 2:27 am by mysticbb

turk3d wrote:True, but the fact remains that if you were to take total points scored at each position for each time and added them up, you'd get the same result. Hence, this becomes a simplified way to find out where the pluses are coming from, as well as the minuses and allow you to attempt to make the appropriate adjustments, by making substitutions in order to improve that outcome (it's just a slightly different way to quantify things).


The conclusion you are drawing about players is wrong. It really doesn't matter at all, whether a player is outscoring a supposed to be direct opponent player in order to make a positive impact. In fact, a player, who has his basic positive impact due to his team and help defense, can even get "outscored" by 10 or 15 points while still being the main reason for the win. Ben Wallace got constantly outscored and yet he had a great positive impact.
The issue is that the players are having specific roles, which are not just determined by their "positions", but also by their skillset and skill level.

turk3d wrote:And also, I agree who cares about the past? What's important is the present and what's going to improve your present situation. Past data sure has it's uses, but during the season you're more concerned about improving the present. One of the problems is that the past doesn't take into account (especially the more years a years a player has behind him) is if/when a guy might be having a breakout year (or for that matter a downer year). I think there could be value in doing it both ways.


Reducing the overall sample might very well lead to the wrong conclusion, let alone that PER has not a very good ability to predict the outcome of games anyway.

Alfred wrote:Because generally, one PG, one SG, one SF, one PF and one C are on the court at the same time. That isn't always the case, but positions do matter.


That doesn't explain that at all. Those "position" do not present a specific role for each player, because that is also determined by the skillset and skill level.

Alfred wrote:Who you are replacing a player with is just as important as how good that player is. If their competition is terrible, then they become more valuable.


No, that is a wrong conclusion. You need to understand the concept of the game before drawing conclusions like that. As DocMJ pointed out, a player does not become a better piece to build around only because the average PER of players who are supposed to have the same position is lower than for other positions. It is a flawed concept, which is not representative for the real basketball game.

Alfred wrote:I don't really see why we should care about the weighted minutes?


Because you want to compare the player to the average value on his position, and that is determined by the minute weighted average not by the simple average.

Alfred wrote:The value of the proposed stat is that it allows you to gauge a player based on the strength of his peers at his position.


You misunderstand the purpose of the stat here, if you think that the stat is meant to be "gauge a player on the strength of his peers at his position". The idea is that PER represents a value, which is supposed to show the overall impact on the outcome of the game regardless of any position.

Alfred wrote:If he is producing at a level that outstrips his competition at that position, his value is higher than someone who doesn't.


That is nonsense within the framework of the game.
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Post#16 Re: Positional PER
Thu Jan 10, 2013 3:28 am by kabstah

turk3d wrote:True, but the fact remains that if you were to take total points scored at each position for each time and added them up, you'd get the same result. Hence, this becomes a simplified way to find out where the pluses are coming from, as well as the minuses and allow you to attempt to make the appropriate adjustments, by making substitutions in order to improve that outcome (it's just a slightly different way to quantify things).

What you say is true but it has nothing to do with positions. You can pair off players from two teams any arbitrary way you want -- closest birthday, closest jersey number, whatever -- and the cumulative differences from each pair will still sum up to the total difference between the teams as long as there are no unpaired players.
Alfred wrote:I don't really see why we should care about the weighted minutes?

Because PER is a per minute rate stat. If I asked you to calculate league FG% would you just give me a straight average of the FG% of all 400+ players or would you weight by number of attempts? If Lebron, PER of 30, plays 40 minutes at SF and is backed up by Shane Battier, PER of 9, for the remaining 8 minutes, do you think a positional PER of 19.5 accurately represents the level of play at SF?
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Post#17 Re: Positional PER
Fri Jan 11, 2013 5:10 pm by turk3d

turk3d wrote:True, but the fact remains that if you were to take total points scored at each position for each time and added them up, you'd get the same result. Hence, this becomes a simplified way to find out where the pluses are coming from, as well as the minuses and allow you to attempt to make the appropriate adjustments, by making substitutions in order to improve that outcome (it's just a slightly different way to quantify things).

kabstah wrote:What you say is true but it has nothing to do with positions. You can pair off players from two teams any arbitrary way you want -- closest birthday, closest jersey number, whatever -- and the cumulative differences from each pair will still sum up to the total difference between the teams as long as there are no unpaired players.

I suppose, but why not go by positions? Would you rather compare a Center to a 2 guard. There are some caveats in doing it this way but all it is is a methodology that we're talking about. Even though there are a lot of position variations now in the NBA (more and more it seems) the variation isn't that much as typically you are talking maybe one position over, and that can easily be accounted for.

For example, a PF might play C/PF but unlikely will play PG or shooting guard) you'd just have to do a breakdown if the player is playing more than one position and you could get more accuracy that way. As a matter of fact you might find that the player is a plus at one position and a minus at the other which can help a coach determine where guys should be playing.

And yes, no matter how you break it down position wise (or even using some other method) the point totals will be the same, but what will it tell you that the boxscore (actually final score) wouldn't tell you. This way you'd be able to tell what positions are giving you the best and worst results.

kabstah wrote:The conclusion you are drawing about players is wrong. It really doesn't matter at all, whether a player is outscoring a supposed to be direct opponent player in order to make a positive impact. In fact, a player, who has his basic positive impact due to his team and help defense, can even get "outscored" by 10 or 15 points while still being the main reason for the win. Ben Wallace got constantly outscored and yet he had a great positive impact.
The issue is that the players are having specific roles, which are not just determined by their "positions", but also by their skillset and skill level.

Ben Wallace was many times a net positive because guys who may have had better numbers scoring wise overall were shut down by him because he was such a great defensive player. It doesn't necessarily matter if you are a high scorer, what matters is whether you can outscore your opponent or even by how much (you outscore your opponent by just 1 pt and the rest of your teammate break even, you win).

Eleven time all defensive player and 4 times defensive player of the year. Just because his point total may not have been too high, doesn't mean his net point total wasn't in the positive in most cases.

kabstah wrote:Because PER is a per minute rate stat. If I asked you to calculate league FG% would you just give me a straight average of the FG% of all 400+ players or would you weight by number of attempts? If Lebron, PER of 30, plays 40 minutes at SF and is backed up by Shane Battier, PER of 9, for the remaining 8 minutes, do you think a positional PER of 19.5 accurately represents the level of play at SF?

If the sum total +/- for Battier is > than the sum/total +/- for the opposition, then the Heat are winning the position and that's all the matters in this scenerio. Do the same for all 5 positions and this will tell the tale for the entire team. Just another way to measure individual success. You can always play Lebron more minutes or replace Battier if he's losing his battle with opposing 3s if you have a replacement.
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Post#18 Re: Positional PER
Sat Jan 12, 2013 3:06 am by mysticbb

turk3d wrote:I suppose, but why not go by positions? Would you rather compare a Center to a 2 guard. There are some caveats in doing it this way but all it is is a methodology that we're talking about.


Because the game is not about a single player outscoring the supposed to be direct opponent player, but that a team outscores another team. It is a team game, 5on5, not 5 individual 1on1 games. Thus, any kind of comparison based on "positions" is flawed and is not within the context of the game itself. That has way less to do with overlapping positions than much more with the concept of the game.

If you have metric, which is able to measure the impact on the outcome of the game, you should be able to use it to compare a SG vs. a C, PF with a PG, etc. pp., because the metric should incorporate everything already.

turk3d wrote:Ben Wallace was many times a net positive because guys who may have had better numbers scoring wise overall were shut down by him because he was such a great defensive player. It doesn't necessarily matter if you are a high scorer, what matters is whether you can outscore your opponent or even by how much (you outscore your opponent by just 1 pt and the rest of your teammate break even, you win).


Ben Wallace points per 48 min vs. points per 48 min of his supposed to be direct opponent at C:
2003: 8.6 vs. 15.8
2004: 12.2 vs. 13.5
2005: 12.9 vs. 15.5
2006: 9.9 vs. 16.1
2007: 8.8 vs. 17.1
2008: 7.5 vs. 19.0

The direct opponent of Ben Wallace constantly scored more points than Ben Wallace. Ben Wallace never was the great 1on1 defender you make him out to be, his strength was team, help and weakside defense. When the Pistons aquired Rasheed Wallace, Rasheed would usually defend the better post player 1on1, because he was better than Ben at that.

Ben Wallace is the perfect example of the flawed concept you are trying to use while missing the point kabstah made. You can pair up players by any weird criteria and it will just end up with the correct result anyway. The test you apply in order to justify your method is flawed and will not tell you anything at all about the players and their impact on the game.

turk3d wrote:You can always play Lebron more minutes or replace Battier if he's losing his battle with opposing 3s if you have a replacement.


No, you can't do that. Battier's job is not to replace the production and efficiency of James, but to give James rest while still providing useful skills in order to make the team win. The responsibilities of James are shifting to other positions, players like Bosh or Wade are taken over more offensive load in such case. Again, the game is not about 5 single 1on1 games, but just one 5on5 game. Players are picked to play certain roles, provide certain skills, in order to make the team work together to win the game. How the boxscore entries are distributed among those players is not that important. If the presence of a player, who doesn't produce much, but is doing all the little things not captured in the boxscore, can enable his teammates to be in better positions on the court in order to increase the overall efficiency difference of the team, he can lose the "battle on his position" while still being a key factor to the team's overall performance level. Derek Fisher was such a case for the Lakers, Ben Wallace was one for the Pistons, Bruce Bowen for the Spurs, etc. pp.
But that wasn't even the point kabstah made. He explained to Alfred why a minute weighted average has to be used and not a simple average. Alfred compared the simple average of the different "positions" presented by hoopdata. The simple average pcitured the difference to be much bigger than it really is.
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Post#19 Re: Positional PER
Sat Jan 12, 2013 11:01 am by turk3d

Mathematically it works. It's value may be questionable. And you'd have to delve into it in more detail to get definitive results. It would be just one more analytic (all seem to have their associated flaws so I don't see anything different).

It certainly gives you more of an "apples to apples" comparison and I think is probably a better way to compare players (considering that teammates can make a guy look better (is he making his team better or is his team making him look better?).

Yes basketball is a 5 on 5 game but it is the aggregate of those 5 players which determine who wins or loses and if you outscore your man (and so do your teammates), you win. It's academic no matter how you wish to slice it. I hate it when you compare players who have different teammates, different coaching styles and claim that "so and so" is better than "so and so".

Swap teams and you might see a totally different result. That's why I like the idea of looking at who wins the head-to-head matchup. It tells me a lot more about a player than some of these advanced stats being used. Do you outscore your man or does he outscore you the majority of the time?

Ben Wallace is the exception here. He constantly beat his man in rebounding and he was a great help defender (Positional metric doesn't take this into account) but it still says a lot.

In Wallace case, I want to know what his +/- was when he led the league in rebounding (2001, 2002 and even 2000 when he averaged 13.2) . And I'm not interested in his per 48 that much (he didn't play for 10 or more mpg on average). You seem to be factoring in someone else play at the position and I'd like to see what their +/- was.

It might look considerably better than the numbers you've posted (don't really know but certainly could be). Per 48 does show us the difference from the position for a full game, but we can't really tell what player(s) the negative numbers came from and to what extent. Regardless, I think Wallace is the exception.

We can still do the metrics which show overall team effect and the coach can decided to keep a guy who may be somewhat negative in the plus/minus in the lineup based on other data should he feel his positive impact in other areas is > than his lack of scoring.

Probably can say the same in today's game about Chandler who may frequently get outscored but provides so much to the team in other ways, although he does shoot almost 70% from the field. I'm not going to argue that this is better than what we already have, just that I believe this could probably give us some additional insights.
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Post#20 Re: Positional PER
Sun Jan 13, 2013 4:02 am by mysticbb

turk3d wrote:Mathematically it works.


Nobody is denying that, but it is a fallacy to use that working math to justify the method, because it doesn't work mathematically due to a sound method. That's what kabstah pointed out when he wrote that "you can pair off players from two different teams in any arbitrary way you want", it will always sum up to the result.

turk3d wrote:It certainly gives you more of an "apples to apples" comparison and I think is probably a better way to compare players.


It is not a better way to compare players, it just a more convenient one. If you have a metric which is able to determine the impact on the game results by a player, it should be independent on the "position", and thus no arbitrary pairing off of players is necessary at all. If the metric is really way different between positions, such difference is pointing to a flawed metric, and any kind of positional adjustment or such comparison will not lead to a better metric here at all, the metric will still have the same flaw. PPG is just not a good metric to compare the overall impact of a player, no matter whether you compare all players regardless of "positions" or just players from "one position". The amount of shots a players get is not just determined by the individual player alone, but by the overall team offensive concept as well as the defensive concept of the opposing team.

turk3d wrote:It's academic no matter how you wish to slice it.


There is nothing academic about that at all, if you count up all the points one team scored and compare that to all the points the other team scored, it will always show the result no matter what kind of pairing you want to use. That is the simple concept of the game, count the overall score for both teams and the one with the higher score will win. In fact, that is the concept of basically all team sports. But pairing off the players from different teams is not giving you a better analytical tool.

turk3d wrote:I hate it when you compare players who have different teammates, different coaching styles and claim that "so and so" is better than "so and so".


You can hate that as much as you want, but a tool which allows the comparison of players regardless of differences in team structure, coaching styles or positions is exactly what decision makers need. Everything else is just fooling around without gaining real important informations.

turk3d wrote:Ben Wallace is the exception here. He constantly beat his man in rebounding and he was a great help defender (Positional metric doesn't take this into account) but it still says a lot.


Team defense and help defense is ignored by any boxscore-based metric, because there is no entry for that in the boxscore at all. Thus, you will always fail here. And Ben Wallace is not the lone exception, there are many players like that who still helping their teams win more games. The issue is not that an individual player must score more points than the opponents players on the "same position", but that a player must enable his team to score more points than the opponents overall team. A facillitator on offense, in an offensive system like the TPO for example, will basically getting no credit for initiating the offense at all, but he is as important to the system as the post guy scoring the points. There are multiple defenders in the league on all kind of positions which are in there for their team and help defense. That doesn't show up in boxscores for them individually, just in the end, when we look at the result. If your metric is not able to deceiver the defensive contribution, it will fail and it doesn't matter whether you just compared players from supposed to be one position. If the metric can deceiver that and can give credit accordingly (like some version of APM might be able to do that), no positional adjustment would be necessary at all.

In the end, what you are trying to justify is the usage of a bad metric by proclaiming that when used just in a comparison for players from the "same position" would magically become a better metric. But that is a flawed thinking.

turk3d wrote:Probably can say the same in today's game about Chandler who may frequently get outscored but provides so much to the team in other ways, although he does shoot almost 70% from the field. I'm not going to argue that this is better than what we already have, just that I believe this could probably give us some additional insights.


Chandler is nothing like Ben Wallace, there are not even close. Chandler is far worse in terms of defensive impact, does neither possess Wallace' ability to defend 1on1 nor has his team and help defense strength. Chandler's biggest contribution is already captured by the boxscore, his ability to catch the ball and convert at a high rate. As long as Chandler does not need to create offense for himself or others, he is not turning the ball over. Wallace had weaker hands.
There is no additional insight gained by comparing players from the same position, if the used metric is flawed to begin with. That is an important point, a point anyone must understand otherwise any kind of player comparison based on stats will be prone to fail.
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