Looking into the Defense

Promoted FanPost

The Boston Celtics have the best defense in the NBA this season. I just wanted to look into some of the noteworthy numbers behind this accomplishment. I feel the best way to evaluate defense is to look into Defensive Rating. It's basically a way of evaluating defense that takes everything into account: pace, offensive rebounds, turnovers, and free throw attempts allowed. Seems that every broadcaster lives in the stone age when they say definitive statements like "Chicago has the lowest field goal percentage allowed and are the best defense in the league." A team might have a very low fg% against, but they never cause turnovers. Why should turnover causing teams be penalized? I'm not even going to say anything about points per game allowed because I don't even think there's anyone left that would argue that. They probably exist, but probably checked out mentally when they read the word "pace." Just too much for their minds to comprehend.

Monthly Splits - try to keep in mind that lower is better when it comes to DRtg

October/November: 99.72 DRtg 13-4 (.765 winning pct)
December: 97.84 DRtg 11-3 (.786 winning pct)
January: 101.79 DRtg 12-4 (.750 winning pct)
February: 98.22 DRtg 7-4 (.636 winning pct)
March (up until 3/27): 98.72 DRtg 8-6 (.571 winning pct)

What can we read from this? Well, looks like the defense has been pretty consistent the whole season. The defense has been just as good in the late season slumping. January was the only month where the boat rocked for the defense and KG missed half of the month with the calf strain. It becomes very obvious very quickly when looking through the numbers that KG is the number one factor in the team's defensive success.

DRtg for games with KG in the lineup (62 games): 98.31
DRtg for games with KG out of the lineup(10 games): 106.08

Very significant! 98.31 would be tops in the league. 106.08 would be 15th in the league. Also noteworthy that the games he missed were not against killer offensive teams. The average ORtg ranking of the teams they faced during his missed time was 17th(about league average.) I know there are certain holes in this, though. There is a butterfly effect. KG out means that bad players seep into the rotation. Specifically a bad defender like Luke Harangody. Based on's Numbers, we are able to see that the team had a 104.75 DRtg when he was on the court with Boston for his 241 minutes. Most of those 241 minutes came during KG's absence. So, Luke filling in the rotation for that time period definitely made the numbers worse, but KG's defensive star still shines bright nonetheless. Solid defender Jermaine O'Neal also was getting minutes during KG's hiatus and he, despite his awful reputation around the Celtics blogosphere has a 99.65 Defensive Rating while on the court. The guy still defends pretty well.

Perk and the Trade
Can't do a Celtics piece at this time without heavily mentioning that drastic trade. It's some sort of unwritten rule. Let's start it off with this:

Celtics Before Perk Returned From his Injury this season on January 25th: 100.21 DRtg (would put them at 2nd in the league)
Celtics When Perk Returned (12 games): 97.05 DRtg (would be 1st in league)
Celtics Since Perk was Traded (17 games): 98.97 DRtg (1st yet again)

What is there to learn from these numbers? Perk is obviously a great defender, but how needed is he to making the Celtics elite? The Celtics D is elite with or without Perk. Those 17 games since trading Perk tell a major story in my eyes. Especially when you consider the centers in that time frame have been Nenad Krstic, Glen Davis, and Chris "Beanpole" Johnson. Offensive rebounding allowed is in these numbers, too, so you can't even blame the recent slump on clearing the defensive glass. 4 offensive rebounds in one trip down the floor count as one possession.

I'd definitely argue that you have to look elsewhere for the blame on the latest struggles. Unless you think Perkins would be a major help on the offensive end, but I think that post is for another time. We can visit that later.

Tidbits Found:

Home DRtg: 100.39  29-8 record (.784 winning pct)
Away DRtg: 98.33 22-13 record (.629 winning pct)

The team is better on D on the road...very interesting. Also clear that the offense must be truly screwing up on the road.

Second Night of a Back to Back(15 games): 102.13 DRtg
Every Game that is Not the 2nd Night of a Back to Back(57 games): 96.97 DRtg

I looked for information regarding league wide B2b performances and came up pretty dry so I don't know how significant this is, but I found it to be interesting food for thought nonetheless. On the surface it has to warm the heart of Celtics fans since the playoffs are B2b-free.

Had fun doing my first analytical post. I plan to do an offensive one within the week as well. I suspect the offense post will be much juicier since that's where the issues lie currently. Preview: Jeff Green's got a 59% TS for the Celtics so far!

Feel free to give feedback, ask questions about that data, or request that I delve into a certain point.

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