One of the most peculiar NBA stories I remember coming across in recent years was Matt Moore’s piece on why the 2016-17 Spurs were better defensively when Kawhi Leonard—a two-time Defensive Player of the Year who is probably the best perimeter defender of his generation—was on the bench. It represented a clash between the eye test, which obviously revealed that Kawhi Leonard looked like Kawhi Leonard on defense, and analytics, which said that Leonard had the worst individual defensive rating on his team.
However, the truth was somewhere in the middle, and context was needed to find the truth. The truth was that Leonard was still a fantastic individual defender. Yet teams had begun to scheme offensively in such a way that they took both him and his matchup out of the play so that they could effectively play 4-on-4 without worrying about his length and defensive instincts.
If the eye-test is telling one story, but the analytics are telling another, it’s important to remember that neither are necessarily wrong. It just means that more context and nuance is required in order to fully understand the actual reality.
That being said, the Memphis Grizzlies have a fascinating statistical paradox of their own with Jonas Valanciunas, particularly on the defensive end of the court. How is the Grizzlies’ defense better when Valanciunas, who appears to struggle defensively according to the eye test, is on the court as compared to when he is off? The Grizzlies give up 3.8 fewer points per 100 possessions when he’s on the court.
This is all the more head-scratching when you consider that Valanciunas has played over 68% of his total minutes with Ja Morant, who has been the statistical equivalent of a traffic cone on defense this year. And while Dillon Brooks and Kyle Anderson, the two players that he has played with the most this year, are excellent defenders by both analytics and the eye test, I don't think there’s any evidence to suggest that they are over-compensating for him. After all, bench lineups with Xavier Tillman, a generally superior and more versatile defender (more on that in a minute), at center also usually have an arguably elite defender in De’Anthony Melton as well as other capable defenders like Desmond Bane and Brandon Clarke.
So what gives?
First, let me qualify everything I’m about to say by stating that the eye-test doesn’t lie. Valanciunas does greatly struggle to defend in space, and he allows an unfortunate amount of open shots at the top of the paint and mid-range specifically as a result. But I do think that lateral mobility in centers is overrated to a certain degree. It’s definitely a good thing and will only increase a big man’s versatility to fit in various defensive schemes.
However, can a more traditional center/big man who is a dominant rebounder, an effective rim protector, and used properly within the team’s scheme have a positive impact defensively? Jonas Valanciunas would seem to indicate so.
In order to mitigate Valaciunas’ overall lack of lateral mobility, the Grizzlies (like many other teams in the Association) deploy drop coverage, which is when the big man “drops” toward the rim after the initial ball screen, and the on-ball defender usually fights to get over the screen. It’s designed to reduce open threes, discourage shots at the rim, and also encourage teams to shoot more inefficient shots from the mid-range.
According to this scheme, Valanciunas is doing exactly what he’s supposed to do. Opponents take 3.2% fewer shots at the rim when he’s out there and 3.3% more shots from the mid-range. He also does a fine job of using his size to alter opponents’ shots that are taken at the rim, as he ranks in the 76th percentile with opponents shooting shooting 58.6% at the rim. The eye test, of course, doesn’t lie, and opponents are shooting 4.2% better from the mid-range when he’s on the court because of how far he drops underneath the basket. Yet opponents also shoot 3.5% worse from three when he’s on the court, which more than balances the impact in favor of him and demonstrates that the scheme functionally works for the most part.
His dominant individual rebounding is vastly underestimated when it comes to defensive value as well. There’s a reason why Valanciunas was an overall more impactful defender last year than a more versatile defender but far inferior rebounder in Jaren Jackson Jr. Senior staff writer Justin Lewis did a superb job of diving into Valanciunas’ dominance on the glass last week, and an important number from that piece is that he rebounds just over 33% (!!!) of opponents’ misses, which ranks 2nd in the league.
The Grizzlies got a good taste two nights ago from Nikola Jokic of how defensively debilitating it can be when you can’t keep the other team off the offensive glass. Valanciunas, on the other hand, dominates the glass and singlehandedly takes away extra possessions from the opponent. And he’s not just padding his stats by taking away rebounds that would be available to others; the Grizzlies rebound 11.9% more of available misses when he’s on the court as compared to when he’s off.
Contrary to the popular blog-boy opinion, mob-mentality rebounding is a myth. The absence of Jonas Valanciunas doesn’t mean that everyone in the lineup magically becomes better rebounders, even if some of them may rebound more out of necessity, anymore than the Warriors suddenly become better shooters who take and make more shots when Stephen Curry is out of the lineup. To be sure, the Grizzlies need Valanciunas on the court to be a great rebounding team. And when he’s not, they struggle to rebound, giving their opponents more opportunities to score which obviously hurts their defense.
Now, is Valanciunas the best defender in the world? No, he’s not. His lack of lateral mobility generally restricts the Grizzlies to a single scheme defensively and can make them predictable.
Xavier Tillman, however, is a solid rim protector with impressive lateral agility that gives the Grizzlies the chance to wield multiple defensive schemes, including straight-up switching. His lack of size may lead to him getting brutalized in certain matchups like Jokic, but the Grizzlies are able to better create turnovers and get into passing lanes when they're able to switch with him. They create 3.4% less turnovers when Valanciunas is on the court as compared to when he’s off. This is reflected by individual stats as well, as Tillman has a STL% of 1.8 (85th percentile) and Valanciunas’ is 0.7 (18th percentile).
But even though someone like Tillman provides his own defensive advantages, a more traditional center like Jonas Valanciunas brings defensive value of his own. There will be games where his struggles to defend in space are on painful display. Yet on most nights, his combination of discipline, effective rim protection, and tenacious rebounding are more than enough to make him a plus defensively.
Always trust your eyes. But remember, they may not be able to tell the entire story.