I just read a definition and “defensive RPM” seems like a horseshitee metric.
Essentially, it adjusts nominal “plus minus” for the quality of defenders the player is on the court with. Rationale being if Draymond Green, Rudy Gobert, and James Harden are on the court at the same time, Harden is going to look like a lock down defender, when the credit really goes to Green and Gobert. But ultimately, I think the adjusted “real” metric ends up hurting the guys who play with elite defenders. It also ignores how two defenders can complement each other (treats it as a zero sum game).
We can tell from our own two eyes, Donovan has long arms that make it difficult for opposing offense, he gets big steals at big times, and can block shots. Most importantly, he is always hustling on defense. The one thing I would like to see him improve on is early foul trouble. Sometimes he can stack up 3 in a row in the first quarter.