Okay looking at the defensive side of this, I'm seeing some red-flags:
How does Box Plus/Minus evaluate players? The basic concept is simple. BPM starts by assuming that every player on the team has contributed equally. If the team is good, all of the players are assumed to be equally good.
Next, the box score information is added to revise the evaluation. All of the box score data is measured relative to the other players on the team. Does this player get more or fewer steals than the other players on the team? If more, this player is likely better on defense than they are. Do they score more or less efficiently? Do they have more or fewer assists?
To be blunt, getting a bunch of steals has very little correlation with good defense, on a team, or individual level. Last season for example, of the 6 teams with the most steals per game, 3 had good defenses, 1 had an average defense, and 2 had a bad one.
Looking at last seasons's steal leaders:
https://www.landofbasketball.com/year_by_year_stats/2021_2022_leaders_steals_pg_rs.htm#:~:text=Who%20averaged%20the%20most%20steals,Leaders%20this%20season%3A%2058%20games.
IIRC, most of these players
don't grade out as elite defenders via something like EPM(unfortunately last seasons's EPM data is no longer publicly available so I'm working off memory here). Using the prior defenders who get more steals are likely better than defenders who don't is kind of concerning since, going positionally, guards usually get the most steals, and they also happen to be(at least using a EPM metric as a baseline), the least valuable defensively.
I think what they're doing with blocks here is an even bigger red-flag:
This box score information is also weighted according to what position or role the player has on the team. For instance, a block by a center is good, but a block by a guard is great.
The problem here is that blocks from smaller players are often more a result of a bigger teammate's assistance than vice versa...(from a reddit post by ftd)
OhayoKD wrote:Why would you compare hakeem with pj tucker? The idea is that players who are racking up steals and blocks are going to be treated by box-metrics like dpoy-level defensive contributors, which is why your jordan's, kobe's and curry's look much better relative to other all-time greats when you focus on the box and less so when you focus on how the team defense correlates with their presence. One of the things bigger defensive players do is generate opportunities for smaller to rack up steals and blocks in the first place
We talk about gravity on offense, but what about defensive gravity? As I said before, Ben touches on the concept when he notes that Walton affected more possessions than Kareem despite Kareem getting alot more blocks, but this reaches a whole new level with players like Larry Bird or 6'6 shooting guard MJ, players who spent their defensve primes playng with one or multiple comparable-better rim deterrents.
This is what most jordan blocks look like:https://youtu.be/fFPi95UEpog?t=55 Jordan gets the block, but is he even the key to this possession? The difficult part of this, holding ewing still, isn't being done by Jordan. Jordan is making this play off his teamamte's, gravity defensively. If you rewatch the section where ben is fawning over Jordan's rim protection...
https://youtu.be/p5aNUS762wM?t=1212...you might notice that aside for --two-- clips, all these plays have jordan making plays on a defender whose preoccupied worrying about a larger guy at the rim.
Lets compare this to the following non-blocks:https://youtu.be/T-c1NradPN4?t=147Lebron's presence here blows up a potential dunk/layup, a shot even more dangerous than a curry three. Lebron isn't awarded a block here, but this play is more valuable than the majority of plays you'll see in a jordan defensive highlight reel.
https://youtu.be/T-c1NradPN4?t=17Lebron here basically prevents a open layup/dunk. These kinds of plays are both extremely valuable and require a combination of strength and size Jordan doesn't have.
https://youtu.be/T-c1NradPN4?t=176Here, Lebron isn't rewarded a block and even looks a bit silly, but his presence is what draws draymond's attention and allows for delly to get the block.
https://youtu.be/3oAAcEQ8t84?t=1529Lebron ends up getting a block later on the possessions, but the key of this possession is here, where Lebron's presence makes dwight opt for a post up, preventing what is the most dangerous play in basketball, an all time interior threat coming in at the rim. Per r/blockedbybam, Lebron blocked, diverted, or deterred a dwight inside atempt 18 times over the ECF..
https://youtu.be/MyWFllfRqaU?t=256.Grant gets the block, and pippen is made to look silly, but it's pippen who sets the play up for grant. Much like a shooter will feed of a slasher's interior gravity, grant makes this play off pippen's defense.
https://youtu.be/C7uxePXXfU8?t=63While the possession doesn't end up going chicago's way, what Pippen is doing here, essentially pre-emptively nuetralizing the threat of an Ewing drive is about as valuabe as a play you will get defensively. It doesn't show up in the scoresheet.
Gobert stops a layup here but he doesn't touch it so no credit
Generally, if we look at raw impact/wowy, or even things like LEBRON or RAPM(or even the more boxy PIPM), Guards posting comparable blocks per games to wings usually aren't actually generating more defensive impact. Yet BPM is essentially rewarding smaller defenders for making less valuable plays. This is how you get something like Larry Bird DBPM = Pippen
You have to be aware of the shortcomings of stats like BPM but they still paint a better picture than the raw box numbers. Just going off WOWY type stuff for older eras is too limited imo.
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WOWY may be limited but it isn't going out of its way to skew towards certain positions(let alone a position which everything says is the least valuable), and you can use knowledge/other signals to expand its use. How exactly do you adjust for dbpm without just chucking it? Feel like when possible you should go by impact signals defensively to supplement the offensive stuff, even if you value bpm for "stable" offensive stuff. That alone will probably adjust a bunch of stuff.
Other thing is bpm's formula is based on incomplete data which will bias things agaisnt pre 80's players. Imo, BPM is just there as a last resort and i'd still just look at offense tbh. Defensive stuff is acctively going out of its way to mislead you.