Quick Thoughts on RPM
The context and the noise, which these models work so hard to control for, are exactly the things I’m interested in. I don’t just want to know which player is better. I want to know why and in what ways. I want to know what that implies about both the player and team, his teammates and opponents, and basketball as a whole. As constructed and presented, I typically find precious little of that information in plus-minus statistics.
The Perk Effect
The Memory (and the Bonus) Remains
On the flip side, players who are good at drawing fouls might be undervalued, because their teammates can take advantage of the extra time spent in the bonus, but also because of how the fouls they draw affect the opponents' play. Putting fouls on starting players brings the backups into a game, and forcing the opposition to play their worse players more is obviously helpful in terms of winning the game. Even if these fouls don't cause foul trouble, they can still reduce the aggression with which opponents play out of concern for picking up the next foul and thus being forced to sit on the bench during a normal rotation spot, losing minutes and thus counting stats and ultimate money.
None of this is to say RPM is a "bad stat" but it is not as unbiased or proponents would have us believe, and these effects along with those mentioned in the links above are some of the important caveats to keep in mind.