I commented on Billy being 2nd in coach RAPM on another post. Still not sure what to make of this stat, but this was an interesting comment from the reddit post.
So does it just give Donovan a ton of credit because Westbrook was all-NBA tier on the Thunder and then fell off a cliff right after?
It's probably a combination of a ton of data:
Enes Kanter magically becoming playable in OKC, and otherwise being like the worst player in the NBA
Serge Ibaka falling off a cliff after leaving OKC
Schroder being a 6th man in OKC, then pretty bad after
Zach Lavine turning into All-NBA under Donovan
Gallo having a random great season under Donovan
Lonzo immediately having a really good season under Donovan, after being a little up-and-down in NOLA
Paul George becoming a #3 MVP candidate
Enes Kanter certainly had the best offensive stretch of his career under Donovan. Kanter's 3y RAPM in his last season in OKC (2017) was -0.7, with a career high 2.8 offensive RAPM. DARKO (DPM) also agrees that 2016-17 was Kanter's peak offensively.
Ibaka only played a single season under Donovan. Ibaka's 3y RAPM in 2016 was 3.5, the highest of his career however, that includes two seasons under Scott Brooks. Looking at DPM for the 2016 season, Ibaka had the best DPM of his career in the single season he played under Donovan. Ibaka's DPM drops from 3.2 in 2016 to 0.9 in 2017.
Schroder's last season in OKC (2020) was also his highest 3y RAPM. Schroder's decline is overstated in the comment. He's always been a solid guard, but never good enough to make it as a full time starter. His RAPM drop off isn't that much, 1.2 RAPM in 2020 and 0.6 RAPM in 2025. DPM thinks Schroders' best season was in 2016 over 2020, but the difference is minor.
Zach's prime years were with the Bulls, so instead I'll look at Zach's single season DPM under Boylen compared to under Donovan. Zach had a DPM of 0.4 in 2020 and 1.8 in 2021. While most of the roster remained the same over these two seasons, I can't say how much of Zach's improvement is better utilization vs player progression.
Gallo was a good player, so I wouldn't call it a random good season. He was effective the year prior under Doc Rivers. DPM thinks he had a better season under Donovan than Rivers, and Gallo declines significantly after leaving OKC.
Lonzo had his best season under Donovan, but given his short career at the time, I wouldn't think much of it.
PG has his best 3y RAPM and DPM in 2021 on the Clippers. Injuries and expectations probably cloud how effective PG was on the Clippers. Statistically, his best season was under Donovan, and other metrics might think his best season was in 2019.
Not a perfect way of doing things, but notable players do seem to have their best stretches under Donovan.