NBA Playoffs: The Celtics' rebounding issues vs. the Bulls start with their guards

The Chicago Bulls have destroyed the Boston Celtics on the glass in their first-round series to take a 2-0 lead. The gap isn't as wide as you might think; the Bulls have 32 offensive rebounds to 23 for the Celtics. But Chicago is grabbing 39 percent of all of their own misses, a huge number, by far the most in the playoffs. They have 10 more second-chance points. It has been a problem. 

In Game 2, the Bulls and Celtics both had 11 offensive rebounds, but the fact that the Bulls have still gotten so many second-chance opportunities is giving the Celtics issues. 

Let's start with the obvious stuff. Some of it is just horrible effort. Much of it is impacted by Isaiah Thomas' size. Here he just ducks out of the way in transition, and there's no effort to even try on the defensive glass, whether because of his size or whatever. 

It's not just Thomas. He's here and does nothing, but neither does Jaylen Brown. Look at how many Celtics are there to get this rebound, and how none of them do. 

Then there's this sequence, where, again, the guy Thomas is guarding attacks the rim and Thomas just can't do anything:

Here, Al Horford has to leave his man (Nikola Mirotic) to contest on the rebound by Thomas' cover, and when he does, that frees up Mirotic for the putback. 

Thomas gives great effort here, trying to snag the board after he's switched onto Robin Lopez, but ... he's just not big enough, and this is easy for Lopez:

Speaking of Lopez, sometimes he's just flat-out dominating his one-on-one matchup. Kelly Olynyk gets worked here:

All of this points to a problem that's more complicated for the Celtics than most are making it out to be. The Celtics' defensive rebound rate is at its lowest when Amir Johnson is on the floor, but as seen above, Johnson isn't actually involved in all that many of the offensive rebounds allowed. He's sometimes drawn away from the board by having to battle Lopez, but in those situations, the guards have to snag those boards, and they can't. 

Take a look at the difference when a player is on and off court in second-chance points per 48 minutes and opponent offensive rebound rate: 

Celtics on/off court differential (higher means worse with player on floor)

2nd chance Points per 48Offensive Rebound% allowed
Bradley,Avery23.625.60%
Brown,Jaylen-11.16.50%
Crowder,Jae-1.2-5.50%
Green,Gerald-19.6-39.50%
Horford,Al146.70%
Jerebko,Jonas-19.3-40.00%
Johnson,Amir21.912.70%
Olynyk,Kelly-11.92.80%
Rozier,Terry-12.7-28.80%
Smart,Marcus-11-12.40%
Thomas,Isaiah4.49.20%
Young,James-18.8-39.00%
Zeller,Tyler-2.2-5.90%

Johnson has the highest offensive rebound rate allowed when he's on the floor (46.7 percent). But Avery Bradley and Thomas both have similar numbers, and their minutes overlap. 

Thomas has been dealing with the tragic death of his sister. Just the fact that he's on the floor at all is a testament to his love of the game, his professionalism and his commitment to his team. He has played admirably despite the circumstances, and deserves empathy and understanding for his situation. What these clips and this data really indicate is something we touched on in the regular season: The Celtics' roster is poorly built to compensate for his unavoidable shortcomings on defense and rebounding. 

The Rajon Rondo injury -- he is out indefinitely with a fracture in his thumb -- throws a huge wrench in this however. As seen above, the Celtics tend to over-help when Thomas faces a huge size mismatch. Without Rondo pressuring him in the post, the Celtics might be able to mitigate that issue. And none of the other Bulls guards are adept at offensive rebounding the way Rondo is. That injury could very well flip the series. 

Additionally, the Celtics can just give better effort. Expect to see some different combinations of players to try and negate these issues, but just bringing an energy and a focus on getting to the ball first can lower the Bulls' advantage. That, combined with Rondo's absence and a regression to the mean for the Bulls' shooters could be enough to get the Celtics back in this series. 

But what this means going forward in the playoffs is far more concerning, because they will face better teams, with guards who are just as good, and excellent interior players, as these playoffs go on. Boston's rebounding woes aren't going away any time soon, even if the Celtics survive the Bulls. 

CBS Sports Writer

Matt Moore's colleagues have been known to describe him as a "maniac" in terms of his approach to covering the NBA, which he has done for CBS Sports since 2010. Moore prides himself on melding reporting,... Full Bio

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