Why it's time to start worrying about the Celtics rebounding again

Even back in October, Brad Stevens wasn’t quite sure what to expect from his team’s rebounding this season.

“The defensive rebounding has been pretty good,” Stevens said after watching his team during the first week of training camp. “I don't know if that's because we are not rebounding as well offensively, because now we are all of a sudden a great defensive rebounding team. That's the beautiful part about intrasquad scrimmages -- something is going well, you know? I can't tell yet (with the rebounding) but I think our long wings help.”

On paper, the Celtics didn’t do a ton to address the defensive rebounding shortfall that had plagued this team throughout the last three seasons (three straight finishes in bottom five of the NBA in defensive rebounding rate). Aron Baynes was a nice upgrade at center over Amir Johnson on the glass, Daniel Theis had solid rebounding numbers in Europe, Jayson Tatum was above-average on the glass in college, but there were no other meaningful upgrades in this area on the roster. Danny Ainge has always emphasized all-around players over bigs that were strictly rebounders and Stevens always has had to make the best of that handicap on the glass.

Somehow, over the first 18 games of the regular season, this new-look Celtics roster turned into one of the best rebounding teams in the league. In the midst of the team’s 16-game winning streak, they ranked No. 1 in defensive rebounding rate (82 percent) and No. 2 in total rebounding rate. Al Horford was rebounding like he was 25 again (21.4% DRR). Jaylen Brown and Terry Rozier were grabbing boards at a closer rate to an average power forward rather than a guard. The true centers (Baynes, Theis) were holding things down in the middle. It was a well-oiled machine on a nightly basis.

However, since that 16-game winning streak ended on Nov. 23, things have slowly been falling apart on the rebounding front. Over the past 19 games, the Celtics have posted the second-worst defensive rebounding rate in the entire league, grabbing just 75 percent of all available defensive rebounds. That’s a number on par with their bottom-five defensive rebounding rate last year. Theis and Baynes have remained steady with their numbers on the glass, but the rest of the roster has seen notable dropoffs in their rebounding rates (Horford and Brown chief among them).

The sharp regression was on display during Monday’s Christmas night loss to the Wizards as Washington piled up 14 second-chance points off 10 offensive rebounds in the second half. Things got so bad that the Celtics couldn’t even manage to grab a defensive rebound during the final 6:56 of the contest as the visitors manage to score, grab an offensive rebound or turn the ball over during each possession of a 21-8 run to end the game.

So how the hell did the Celtics come up empty on the defensive glass for nearly seven minutes?

“The wing rebounding on the offensive glass,” Brad Stevens said after the game. “I mean, those are killer possessions when you have a stop and you just can’t finish that stop. You know, we turned and looked instead of blocked out most of the night, and it ended up costing us.”

So who were the biggest culprits on Monday night? Let’s turn to the film to find out. Before we do, an important thing to keep in mind: As pathetic as the Celtics rebounding numbers were, they didn’t lose this game because of rebounding by itself. Turnovers (that turned into transition points) were a big issue down the stretch for Boston and the Celtics were overall sloppy defensively as well. A big reason why the Celtics had zero defensive rebounds in that stretch is that they couldn’t manage many stops to begin with.

On the rare times they did, though, they couldn’t end the possession.

“I’m sure that each rebound has its own story,” Stevens said. “But as you go back and look at it, I felt like we were in position to block out quite a bit. We just turned and followed the ball instead of went to the body.”

Offensive Rebound No. 1 (3:14 remaining in fourth)



Jayson Tatum is matched up with John Wall after a switch in isolation. Kyrie Irving is initially guarding Kelly Oubre Jr. on the perimeter but he switches with Marcus Smart as the shot goes up from Wall. Oubre Jr. makes a strong move to the glass and Smart misses the box out opportunity after looking to the shot first. He loses the battle to the ball to Oubre Jr.
Fault: Smart

Offensive Rebound No. 2 (2:56 remaining) 



The Wizards keep running Kyrie Irving through the pick-and-roll until they get a switch. Al Horford is stuck guarding Wall on a jumper while Irving tries to box out Morris, who crashes the glass hard and comes up with the board. He trips himself after grabbing though and falls out of bounds (so he wasn't officially rewarded one).
Fault: Size mismatch/lack of gang rebounding

Offensive Rebound No. 3 (1:21 remaining)



Wall once again has Tatum guarding him in a switch, taking a rebounding weapon onto the perimeter yet again for Boston. He settles for a jumper and Jaylen Brown is caught looking at the shot instead of finding a body to box out. He collides with Markieff Morris on the play (which leads to his injury) while Oubre Jr. grabs the loose ball. The wing dishes to Morris for an easy dunk as Brown hobbles.
Fault: Bad bounce/Brown doesn’t box out his man

Offensive Rebound No. 4 (0:37 remaining)



The Celtics had a chance to make this a one-possession game in the final minute, but were caught sleeping yet again on the wing. Otto Porter Jr. makes a delayed crash of the glass from the corner while Irving has his back turned, waiting for the ball. Meanwhile, Jayson Tatum doesn’t move from his spot just outside the top of the key. Porter Jr. sneaks between both players to grab the board, which essentially sealed the win for Washington.
Fault: Irving/Tatum/mismatch

Fittingly, nearly every one of the Celtics guards/wings were at fault at some point during that horrid stretch. Unfortunately, this is an issue that has been prevalent whenever the Celtics go small at power forward. Take a look at some of the team’s defensive rebounding numbers with their most used lineups that have Marcus Morris or Jayson Tatum playing power forward.