This part one of a two part series about the Celtics rebounding issues. Today’s focus is on the problems. Tommorow will focus on the solution.

Danny Ainge may want to wait for Crowder and Horford to come back before he decides to make any trades. So, he can see if the rebounding issues are starter issues, or bench issues.

The Celtics probably have some of the best rebounding guards in the league, with Bradley, Rozier, and Smart. Their bigs, on the other hand, are not very good rebounders. Johnson, Jerebko, Olynyk, and Zeller all struggle on the glass. If there’s a trade it would likely involve one of those four players.

Amir is clearly struggling on the glass

Amir Johnson has probably struggled more than anyone on the team in pulling in his share of rebounds. His contract also makes him a key part of a trade for matching salaries. His contract is also expiring, which may be something a trade partner would be interested in. Amir is also a really liked member of the Celtics, and does a lot of good things on the floor. His rebounding numbers are often hurt by him having to help out on defense. That usually means that his man is free to get the rebound unless someone rotates to put a body on his man. Excuses aside, Johnson needs to take a lot of responsibility for the Celtics rebounding issues, and really assert himself on the glass, or he could be getting replaced in short order.

Zeller won’t be traded anytime soon

Zeller just signed a deal in the offseason, so he cannot be traded until January 14th. If Crowder and Horford come back and the Celtics can manage their rebounding issues internally, then Ainge may wait until Zeller’s capable of being traded. Zeller’s attraction to potential trade partners is that his contract is not guaranteed next season, so he is potentially an expiring contract.

Olynyk has been OK so far

The Celtics did not offer Olynyk a contract extension, so he will be a restricted free agent after this season. Olynyk is a very good offensive threat as a big, and his outside shooting and ball handling helps stretch out the defense. Olynyk is also a better defender than he typically gets credit for. He has posted a positive defensive box plus minus (DBPM) rating in his first three season, which says he is an above average defender. He might not get a lot of blocks or steals, but he has been solid with his body control, and cutting off angles. Olynyk can help this team win, but if Ainge does not plan on signing him this offseason, Olynyk may get a decent return if the team trading for him is interesting in offering him a contract in the offseason.

Jerebko’s versatility may make him less likely to be traded

Jerebko is an unrestricted free agent after this season. His combination of perfect hair, solid defense, and outside shooting make him a very good 10th or 11th guy to come off the bench. He has struggled at times this year, but, in the past he has been very versatile for Brad Stevens. If the Celtics think Jordan Mickey is ready to step up and take on Jonas’s role, then he could be dealt relatively soon.

Let’s take a look at where all the Celtics stand statistically in the rebounding department

Defensive rebound percentage is the real key stat to look at here. The problem the Celtics have been having is giving up too many second chance points. Offensive rebounds are really a luxury, but not getting offensive rebounds doesn’t hurt the team much.

Crowder is clearly missed on the defensive boards, as his 23. 5% is sorely needed. James Young has been rebounding really well in short minutes, as well as preseason, but his small sample size makes his high percentage irrelevant until he gets more minutes. Olynyk’s 21% is decent, but he too has too small of a sample size to trust his percentages.

The rest of the team is below 20%, including Jerebko, Zeller, Horford, Johnson, and Mickey. 20% is a really important number because if a team gets every defensive rebound, the team will average 20%. The Celtics average 14. 5% of the defensive rebounds. Which means that slightly over one out of every four defensive rebound opportunities turns into their opponent getting an offensive rebound.

If the starter numbers are reliable when they are healthy, then their defensive rebounding average is 15. 8%. That’s a little better, but Amir Johnson’s 11. 7% really needs to improve. Crowder, Bradley, and Horford average out at exactly 20%. With Isaiah’s expected low percentage of 7. 5%, the Celtics really need another big that can make up for that difference.

Below is the leagues top 36 defensive rebounders, with Crowder being 36th. The minimum amount of minutes played to have qualified for this list is 100 minutes.

Tomorrow morning I will post an article that focuses on getting one of these top 35 players to the celtics.I’ll immediately cross off the names that have no chance of getting traded. Then focus on the ones that are on a struggling team. The Celtics clearly need help on the defensive glass, and Ainge has most likely already contacted other GM’s around the league to find that help.

All rebounding statistics are either directly from or based on basketball-reference.com.