The biggest problem facing these Celtics  is the lack of a point guard, but that’s a story for a different day, since there’s no viable solution on the current roster until Rajon Rondo  returns. Sure, a little more Phil Pressey might help, but is an undersized, undrafted rookie point guard really going to solve this thing?
So, let’s address a problem that Brad Stevens  could possibly bandage with the current roster.
The Celtics are the NBA’s worst defensive rebounding team, allowing opponents to grab 33.9 percent of available offensive boards — a number that would rank among the worst in history over a full season. Opponents attempt 39.3 field goals per game within 8 feet of the basket; only the Blazers (43.3) are worse. The opposition scores 20.8 second-chance points per game; only the Nuggets (23.0) are worse. And just four teams (Wizards, Blazers, Clippers, Bucks) give up more than the C’s 44.5 points allowed in the paint per game.
The C’s interior defense needs work. Vitor Faverani, Brandon Bass , Jared Sullinger, Kelly Olynyk and Kris Humphries are allowing an average of 26.5 attempts at the rim, where opponents are shooting 52.8 percent.
The two biggest offenders, naturally, are rookies. Faverani is allowing 11 field goal attempts at the rim per game. Eleven! Per game! That’s the fifth-worst number in the league. He’s grabbed just 49.2 percent of his 14.8 rebound chances per game. The only other player with as many opportunities to snatch fewer than 50 percent is Al Jefferson , who hasn’t played since aggravating an ankle injury on opening night.
Meanwhile, the opposition is shooting 76.5 percent at the rim against Olynyk. That’s ridiculous. Only two bigs (Trevor Booker, DeMarre Carroll) are worse. And Olynyk snags fewer rebounds per chance than Faverani.
Bass has been the most invaluable of the C’s bigs. They’re almost 20 points per 100 possessions better with Bass on the floor. Opponents are shooting 46.7 percent on six field goal attempts at the rim against Bass, and he’s snatching 65.7 percent of available rebounds. Not bad. Not bad at all. For good reason, he’s started all four games and averaged more minutes (31.8) than anyone else in the frontcourt.
Here’s where the issue begins. As Red’s Army noted , the Celtics are 29.4 points per 100 possessions better with Faverani on the bench and 17.5 better sans Olynyk. Yet, they’re getting more burn than Sullinger and Humphries. Perhaps the Celtics are applying a slow-play strategy, accelerating the maturity of their rookies. But Sully’s part of their future, too, and his performance has been better than both rooks across the board.
And, for some strange reason, Humphries hasn’t played a minute since dropping 14 and eight in the opener as Sullinger sat with a suspension. Hump was a plus-10 in eight minutes alongside Avery Bradley , Jeff Green , Gerald Wallace  and Bass, and then plus-7 in five minutes when Jordan Crawford subbed for Bradley. Those remain the team’s best plus-minus numbers. And Humphries snatched seven contested rebounds against the Raptors, a limited sample size that stands atop NBA.com’s Player Tracking statistics.
None of these guys are great defensively, and perhaps the young guns may improve over time, but at least the rebounding of Sullinger and Humphries allows fewer opportunities for the Celtics to be poor defensively.