Comparing RAPTOR and RPM

When fivethirtyeight.com launched their new all-in-one NBA player ratings before the 2019-20 season, it was very exciting, very exciting indeed. That rating is called RAPTOR.

We can only guess how it’s made or what it means but it does offer an alternative to ESPN’s Real Plus-Minus, which some consider to be the best all-in-one rating. It’s impossible to say which one is more “accurate” (it isn’t but I shan’t be doing it today) but we can compare the two rating systems in how their evaluations of players differ.

The data I’ll be using will be the RAPTOR and RPM for the 2019-20 season as of January 11, 2020. FiveThirtyEight suggests filtering out players who’ve played less than 549 minutes, which seems fair enough, and leave us with 249 players to compare.

Both systems use the same scale for rating - points per 100 possessions - so there isn’t a need to normalize the data for comparison.

Defense

First let’s look at the championship-winning side of the ball - defense.

I’ve highlighted the players with the biggest disagreement. The players RAPTOR likes much more than RPM on defense are all centers or power forwards. RPM favors a more diverse selection of players though most of the players there seem to be point guards or other high-usage offensive players.

Some of the selected players on the opposite side come from the same teams: LeBron James & Anthony Davis, Christian Wood & Luke Kennard, Bryn Forbes & Jakob Poeltl, Jeff Teague & Karl-Anthony Towns & Gorgui Dieng. In a way, this is a disagreement on which player gets the credit for their team’s defense. Has LeBron James been playing far-and-away the best defense in the league or is he above-average and Anthony Davis is among the best defenders in the league? At the other end - is Carmelo Anthony an average defender or one of the worst in the league?

Worth noting also that Dieng and Rudy Gobert are ranked among the best defensive players in the league by both websites, however RAPTOR rates their impact to be twice as big.

Offense

On offense another pattern among the disagreed-upon players emerges.

RAPTOR likes high-usage playmakers that dominate their teams' offense. RPM has a wider selection though we could generalize those players as having low shooting efficiency.

The two rankings agree on the top offensive players, however, like on defense, RAPTOR judges their impact to be twice as big.

Again, you could judge each rating by picking out a player - is Jimmy Butler near-average on offense or among the best in the league? Is Russell Westbrook below average or very good?