When the Cleveland Cavaliers acquired Timofey Mozgov from the Denver Nuggets for two first-round picks, they primarily hoped he'd provide a strong defensive presence in the middle of their woeful defense. The Cavs were 23rd in defensive rating through January 7th, when they pulled the trigger on the deal for the lumbering Russian center. They lacked a good rim protector, or even a passable one. Anderson Varejao wasn't capable before he was lost for the season with an Achilles tendon tear, Tristan Thompson tried hard but lacked the discipline and size to be truly effective, and Kevin Love's defensive intensity was (and still kind of is) lacking. Mozgov was brought in to attempt to fix the Cavs' leaky interior.
So far, Mozgov has lived up to expectations. He's averaging a career-high 1.6 blocks per game with the Cavs, and while their defensive efficiency ranking has only climbed to a still below-average 21st, it has improved from 105.5 points allowed/100 possessions before the trade to 104.3 points/100 possessions since. With Mozgov on the floor, the Cavs are 3.4 points/100 possessions better defensively than when he's sitting, and three of the four most frequently used lineups featuring Mozgov have a defensive rating of under 103, including the current starting lineup, which has an excellent 94.5 defensive rating. Mozgov's impact on the team's defensive performance is obvious, given the overall team defensive stats. But what is he doing, specifically, to cause this improvement? Is he actually protecting the rim in the way many expected him to?
Per SportVU data, Mozgov has defended 8.4 shots per game at the rim in his 19 games as a Cavalier. On those shots, opponents are shooting 45.6 percent, which is a pretty good number. Now, that's well below some truly elite NBA rim protectors, like Andrew Bogut (41 percent) and Roy Hibbert (42.2 percent), but considering the volume of shots Mozgov faces, it puts him in that elite conversation. Mozgov's 8.4 field goal attempts faced ranks 13th in the league, well above the number guys with better numbers like Bogut (7.2 FGAs) and Rudy Gobert (7.0 FGAs) have faced. Of players who face at least eight shots per game at the rim, only Serge Ibaka (41.1 percent), Hibbert, and Dwight Howard (45.3 percent) have been better at defending shots at the rim. He's been playing great defense at high volume, and that's exactly what we want to see.
To further put Mozgov's defensive impact in context, consider the drop-off when it comes to the Cavs' other bigs defending shots at the rim. Mozgov's 45.6 percent is a significant improvement over Thompson's 50.8 percent allowed on 6.9 shots per game, and his numbers put Love's (53.4 percent, 7.3 FGAs) and Varejao's (54.4 percent, 7 FGAs) to shame* Mozgov isn't just effective as a rim protector; he's vital if the Cavs don't want to be a sieve at the rim.
*It's important to note that with these numbers, there are some shots where multiple players are logged as defending the shot at the rim, leading to an undeterminable amount of overlap between the Cavs' bigs. Therefore, we can probably expect Love and Thompson's numbers to get better as they get more time next to Mozgov.
Looking at per-play data from the NBA stats page's Synergy component, Mozgov rates pretty well as a disruptor of post-ups and the Pick-and-Roll. He rates in the 64th percentile of post-up defenders, allowing opponents to shoot just 37.8 percent on these looks, for 0.8 points per possession (PPP). Against PNR roll men, hes better, ranking in the 69th percentile of defenders. Opponents shoot just 36 percent with him defending in this play type, a good sign if the Cavs want to continue to play a little aggressively against the PNR with Mozgov rotating over the top.
Mozgov does have some areas where he isn't great defensively. He's not a good defender in space, as he's in the 40th percentile against isolations. And don't ask him to close out on shooters; somehow he's allowing 1.34 PPP on 38 spot-up possessions for the Cavs, good for the 2nd percentile in the league. That's........bad. And most importantly, while his foul rate has been better as a Cav than it has at any other point in his career, he's still averaging four fouls per 36 minutes, which is a little high. As we've seen, particularly in Thursday's game vs. the Chicago Bulls, when Mozgov gets in foul trouble, it handcuffs the Cavs' defense, and they have a tough time managing without him available. That's always part of the risk you take playing a good rim protector, but if Mozgov can't stay on the floor in the playoffs, the Cavs might be screwed, especially if they come up against a team like the Raptors or Bulls, who love to attack the rim.
Mozgov may not be perfect, but in his time as a Cavalier, he's been a very good rim protector, and has anchored the defense in ways that the Cavs previously could not rely on. As he continues to be a presence for the Cavs, the hope is that his numbers against opponents in space stabilize, that he can potentially steer opponents away from shots at the rim, and that he can continue to develop chemistry with the Cavs' other frontcourt players defensively. So far, Mozgov's been exactly as good as we'd hoped, and he has been a major positive in the Cavs' overall team turnaround.