Celtics Rebounding From Last Year

Last season, the Celtics rebounding resulted in a 1.5 rebound per game deficit compared to their opponent’s total rebounds, placing the Celtics 25^th in team rebound differential.  Of the 16 playoff teams last year, the Celtics had the worst regular season team rebounding differential of them all.  The Mavericks and the Nuggets joined the Celtics as the only rebounding "losers" making the playoffs.  Oddly, the Mavericks and Nuggets turned their rebounding differential to the positive during their playoff stints, and the Celtics remained in the negative.

The low point in the Celtics rebounding woes was undoubtedly Game 7 of the Finals when the Lakers out-rebounded the Celtics by a 53 to 40 margin.   The Lakers grabbed 23 offensive rebounds in Game 7, which helped propel them to the championship victory despite their dismal 33% shooting percentage for the game.  Ouch!

During the off-season, salt was tossed in the rebounding wound with the fact that Kendrick Perkins was going to be out for at least two-thirds of this season due to the knee injury suffered in Game 6 vs. the Lakers.  Hope was further dimmed by Kevin Garnett having a post-rookie season low of 7.3 rebounds per game; conventional wisdom suggested that things were only going to get worse due to the NBA mileage KG has logged.  Then Rasheed Wallace retired, leaving the Celtics with no healthy center to start the season. 

Low and behold, the Celtics managed to stock up in bigs over the summer signing Jermaine and Shaquille O’Neal as well as rookie Semih Erden.  At this point, it’s no secret that the Celtics have improved in rebounding this season over last, boosted by the joint rejuvenation of KG as well as Shaq.  The Celtics rebounding differential has improved by a +2.8 margin from last year to this year, resulting in a net +1.3 rebound per game advantage that ranks 9^th in the NBA. 

So last season's rebounding horror has been buried three times 7 feet deep . . . or has it? 

Doc's Preseason Prescriptions

In the preseason, the Boston Herald article Will Shaq Solve the Celtics Rebounding Woes? by Dan Duggan took aim at the issue.  Doc was quoted as saying the following on the acquisition of the O'Neal's:

 "Hopefully it cures our rebounding woes.  We're not going to have Perk for a while so we went out and we got the O'Neal brothers. We'll find out, but I think that's an area that we've addressed on paper with size."

Doc didn't stop with laying the responsibility of rebounding at the feet of just the front court personnel: 

"I think [Rajon] Rondo and Paul [Pierce] and all those guys have to rebound better than they did last year.  If you looked at our numbers, everyone's numbers were down - not just the bigs, the guards' numbers were down on defensive rebounds. I think everyone has to improve rebounding."

Conversely, Chris Forsberg notes in his Dec 3^rd Celtics:  Second-chance Points ESPN-Boston blog that Doc also stresses to his team that he wants the guards to get back on defense after misses and limit transition points.  It seems to Doc that it is all about the defensive rebounds, thereby limiting their opponent's offensive rebounds.  However, the Celtics do not appear to be too vested in chasing their own misses (see below).

The Four Factors

Before we look at the less than stellar offensive rebounding by the C's, I just want to make it clear that the Celtics don't need be the best when it comes to rebounding, as long as they keep leading the league in effective field goal percentage (eFG%) by a large margin.  Note that eFG% accounts for the scoring value of 3-point shots versus straight FG%.  The Celtics rule in leading the NBA in team eFG% differential (offensive minus defensive eFG%) with a +6.6% differential.  Why you ask? . . . because the Celtics have the NBA-best offensive eFG% at 53.4% and the 2^nd best defensive eFG% at 46.8%.

eFG% is the foremost metric within the Four Factors developed by Dean Oliver of Basketball on Paper fame, and the one that the Celtics have ridden to success during the Big Four era (2007-present).  Given the all-star talent and the defensive leadership that remains despite Thibodeau's departure (anyone shocked by when the Knicks had 85 points on the Bulls at the end of the 3^rd quarter on Christmas?), shooting well and defending has been Doc Rivers calling card with Garnett, Pierce and Allen forming the foundation.

You might ask - what is the relative importance of the other Four Factors compared to eFG%, the other Four Factors being 1) getting offensive rebounds (offensive rebound rate - ORR), 2) limiting turnovers (turnover rate - TOR) and 3) getting foul shots and making them (free throw rate - FTR).  As stated at basketball-reference.com, Oliver suggests that the weights of importance for the Four Factors are 40% Shooting (eFG%), 25% Turnovers (TOR), 20% Rebounding (ORR) and 15% Free Throws (FTR). 

A bit of a controversy exists with regard to the importance of rebounding between the likes of Dave Berri (Wages of Wins), who has a decided emphasis on rebounding, compared to Dean Oliver's system.  If the Celtics success is any indication, it is clear that the value of turnovers, rebounding and free throws pale in comparison to shooting, as the Celtics rank 25^th, 22^nd, and 19^th , respectively, in the team differentials for these lesser factors, while still maintaining one of the best records this year.  It goes to show you that their 1^st rank in shooting differential goes a long way in predicting wins.

One thing I'd like to add that sets this team apart is their league-leading 24.8% assist rate, which is the fraction of possessions that end up with an assist.  This indeed defines the team in terms of their ubuntu mantra of "trust each other" with the rock, as you've heard Doc say courtside so often via microphone.

Team Rebounding

The team history for rebounding rates is provided in the table below.  Note that total rebounds are invariably linked to field goal misses by one team or the other.  Since the Celtics do relatively little of in the way missing, but make the opponents miss a lot, rebounding rate is particularly useful to understanding the Celtics.  The rebounding rate essentially equalizes the number of rebounds available to each team, and then assesses how good the team is in snatching them up, whether they are of the offensive or defensive kind. 

The Celtics have never been a truly bad defensive rebounding team, although as Doc said, the team definitely slipped last year and ended up ranking 12^th in defensive rebounding rate (DRR).  This year has been much better, with the 76.8% DRR being the best in the Garnett-Allen-Pierce era (ranking 3^rd this season).

What is the chink in the armor for this Celtics this year is the offensive rebounding rate (ORR) where the Celtics rank dead last.  This is enough of a drag on the total rebounds that the Celtics have a negative differential rebounding rate, i.e., they are in the lower tier of rebounding - ranked 19^th because they miss out on what otherwise would be their fair share of rebounds on the offensive glass. 

Again there is improvement from last year when they were 27^th in rebounding differential, but you'd like to see the Celtics capitalize on the missed field goals they force, and limit the opportunity for 2^nd chance points.

When it comes to the energy put forth in offensive rebounding, perhaps the team has adopted Ray Allen's short-term memory loss regarding missed field goals.  After all, with the power of positive thinking and skill set that these guys have, you would think that all their shots are going in. 

More Thoughts on the Rebound. . .

• Garnett has said that that he wants all the rebounds, and hearing that from KG must be music to Doc's ears, as the aggressiveness on the boards is what was lacking last year.  KG said:

"At this point, I'm trying to get every rebound out there.  Perk's out, Shaq's out, and I'm telling [Paul Pierce to] get out of there. Semih comes in and he's taking some. It is what it is."

• Shaq tops the Celtics with a 11.3% ORR and Garnett with a 30.1% DRR.  If Shaq would have played in more than 19 of the 28 games this season, this article might have a different tune . . . . of course, if they had Leon Powe and his 15% ORR while healthy and with the Celtics - there would also be a different storyline!

• On the other end of the spectrum, Glen Davis and  Paul Pierce are posting their worst ORR numbers during the last 4 years.  Again - it's a sign that Doc has told the players to punt on offensive rebounds unless the ball happens to hit them in the head. . . .

• The Catch 22 with Paul Pierce is that according to basketballvalue.com, the Celtics have the best offensive rebounding as a team when Paul Pierce and/or Shaq are on the court AND Glen Davis is off the court.  Now Glen Davis should start worrying!

• The good news is that Glen Davis has shifted his focus to defensive rebounding, or else he'd catch hell from KG and Doc!  Davis has the best on-court DRR numbers for the team after Garnett . . . that and the injuries is why Davis is logging the 4^th most minutes on the team this year.  Last year he was a mediocre defensive rebounder and perhaps the Celtics best offensive rebounder - he did read the memo and can stop worrying!
• Rondo is posting his best ORR but his worst DRR - you know what Rondo likes to do - cherry pick and steal those rebounds on the offensive end!
• Ray Allen has his best DRR with the Celtics and improved his ORR from last year - he obviously read the memo.