koolcrud wrote:RPM: Player's estimated on-court impact on team performance, measured in net point differential per 100 offensive and defensive possessions. RPM takes into account teammates, opponents, coaches and additional factors
....wat
Chiming in here, apologies if I'm being redundant:
This is ESPN getting with the times, in the sense that NBA teams have been hiring stat guys to make stats like this for over a decade. Cool that they've taken it mainstream.
"Real Plus/Minus" is basically ESPN re-branding Engelmann's xRAPM, so the stat isn't really new, it's just being re-packaged.
And so you know...I don't like xRAPM in the way Engelmann intended it to be used, or as it's being used here.
This is a stat that factors in everything possible to make the best possible guess as to how much impact a player is actually having...and in doing so it factors in things that are nothing but correlation. For example, aging curves. Because older players tend to be more impactful than younger players once you adjust for box score stats, this stat will effectively give older players a boost. That might be useful for someone who doesn't know anything, but if you know what you're doing you already know which guys are savvy and which aren't and you'll want to factor that in in your own minds.
Additionally, the use of Bayesian priors here mostly means factoring in at least the previous season of play. To be clear, a prior isn't factored in the same way that the stats of the season in question are - the two aren't literally being conflated. This doesn't change the fact though that prior seasons color the results.
So when you read this:
LeBron has been accused of coasting at times this season, and RPM reveals where the charge may have merit.
While LeBron was aptly named to the NBA All-Defensive Team last season, his defensive impact this season has been surprisingly mediocre, at least as measured by RPM (-0.21 DRPM). His rating is consistent with the claim that James has not consistently given his best effort this season on the defensive end.
Does the same hold true on offense? No. Offensively LeBron has been as dominant as ever, and his +8.32 ORPM leads the league by a comfortable margin. This means that despite his less-than-stellar defensive contribution, LeBron's total RPM (+8.11) still rates as the NBA's highest this season.
It couldn't be more wrong. It attempts to refute the allegations that LeBron's impact has been less in '13-14 by using a stat that essentially gives him the benefit of the doubt based on prior seasons...and which has a cousin stat that does NOT color the data the same way. Guess how LeBron looks when you eliminate the priors? LIke a guy who is coasting a good bit this season on offense.
In the end, everyone should be using +/- stats to go along with box score stats and of course observations and critical thinking. If this stat helps people do that it's probably for the best, but it's off to a pretty questionable start.