Are rookies getting better on defense?
Or was the 2024 class just unusually good on that end?
I’m keeping this post unlocked because it’s going to be pretty short, and because it’s mostly just based on my looking up some numbers after a conversation I had in Slack.
A friend (Action Network’s Matt Moore) posited that it felt like NBA rookies had been able to more easily make the transition from college (or overseas) defensively in recent years, and were making more of a positive impact on the less glamorous side of the floor. I wanted to see if that was true.
So, I headed over to
’s Substack and called up his Estimated Defensive RAPTOR numbers, then calculated the minutes-weighted average Defensive RAPTOR for every rookie class since 2000. Contrary to Matt’s belief, rookies have not been getting better on defense lately. In fact, the trend in recent years is on a (very) slightly downward slope.
The slope evens out slightly if you remove the two seasons that look like significant outliers (2001 on the low end and 2005 on the high end), but it is still trending very slightly down. HOWEVER, the 2023-24 rookie class was significantly better than any of the previous five rookie classes, and was the second-best defensive class since that 2005 season, sitting behind only the 2017-18 rookies.
Those trends hold even if you limit the sample only to rookies that actually got significant playing time. Unsurprisingly, those rookies had better defensive numbers than did the entire class in most seasons, but the 2023-24 class still fared better than any since 2005, with the exception of 2018.
So, perhaps the reason it seemed to Matt that rookies have been getting better defensively is because last year’s rookies actually were.
Of course, that sample is heavily influenced by Victor Wembanyama, who had the fifth-best defensive RAPTOR of any rookie with at least 500 minutes played since 2000, and with the exception of Andrei Kirilenko, all of the players ahead of him played at least 1,000 fewer minutes during their rookie season than did Wemby.
To negate the Wemby effect, I decided to look at the share of high-minute rookies that posted a positive defensive RAPTOR, as well as the share that posted a defensive RAPTOR of 1.0 or better, to see where the 2023-24 class stacked up.
This past year’s rookie class checked in seventh in terms of positively-graded defender share, and third in the share of players who posted a defensive RAPTOR of at least 1.0, meaning they improved their team’s defensive rating by at least 1 point per 100 possessions when they were on the floor.
Those seven players were Wembanyama, Amen and Ausar Thompson, Chet Holmgren, Dereck Lively II, Brandin Podziemski, and Trayce Jackson-Davis. Cason Wallace (0.94) narrowly missed the list, and if he’d made it, they 2024 class would have surpassed 2000 and posted the second-highest rate of 1.0-plus defensive RAPTOR defenders.
In short, rookies may not be getting better on defense overall, but last year’s class was unusually good on defense. That was true at least in part because of Wemby, but not entirely.
This is good