One Fish, Two Fish, Stat Fish, Jew Fish

Celtics Defense - Who is Pulling their Weight?

The Boston Celtics last year had the third best defense the NBA has seen since the early 70s, and this year they are performing at the same level. Who is responsible for this? Garnett has a well deserved reputation for defensive excellence, Rondo and Perkins look pretty good given their youth, but both Ray Allen and Paul Pierce had worn the ‘talented scorer that doesn’t try on defense’ mantle until very recently. Yet somehow they’ve combined for a historically efficient defense.

Player defense in basketball is hideously fickle to work with - where team defense is very easy to calculate (indeed, as easy as offense) player defense is a genuine struggle, most notably because there are almost no worthwhile defensive stats to work with. Attempting a way around the problem, I came at things backwards. Instead of trying to figure out Paul Pierce’s defensive contribution through his stats, I figured it out using the stats of the players he was guarding. If I know how much value LeBron contributes on average (if anyone’s interested in my value assessment formula i’d be happy to go into it), then I can compare it to how much he contributed while covered by Pierce, and assert that the difference is in Pierce’s defense. It’s an imperfect method, but it is reasonably accurate in broad strokes. Let’s go… into the numbers (queue the Wayne’s World transition music…)

Rajon Rondo

Strengths: An excellent shot preventer. Opposing PGs lost .55 points a game off their 2 pointers, and .57 points a game off their three pointers. In aggregate, opposing PGs average .08 points less per shot than normal (this counts free throws as well.) He forces a lot of turnovers, creating an additional .38 turnovers in the men he guards per game. He denies his opponents good passing opportunities, at .74 assists per game. He also forces his assignment into more fouls than normal, at .54 fouls per game.

Notstrengths: About average at stopping penetration and preventing free throws - opponents got an average amount of free throws off him. Poor at stopping offensive rebounds on his assignment, to the tune of .12 rebounds above average a game. That’s about it.

Total Value: 1.98 points per game.

Ray Allen

Strengths: Monster shot stopper. Opposing SGs lost .48 points off their 3 pointers, but .91 points off their twos. Good at stopping penetrations, .3 points off of FTs less per game. Opponents get .8 fewer assists per game. His assignments lost a staggering .12 points per shot.

Nonstrengths: About average regarding rebounds, slightly subpar at forcing turnovers (.11 fewer than normal per game) and his assignments commit no more fouls than normal.

Total Value: 2.06 points per game.

Paul Pierce

Strengths: Good shot preventer. Assignments lost .3 points per 3 pointer, and .64 points per 2 pointer. Decent at preventing opposing FTs, at .11 FT points per game. His assignments put up .08 fewer points per shot. He is good at preventing opponent offensive rebounds, at .22 per game. His assignments get .3 assists per game less than normal. His opponents commit .36 more fouls per game.

Nonstrengths: Slightly below average at forcing turnovers, at .09 fewer per game. That’s about it.

Total Value: 1.52 points per game.

Kevin Garnett

Strengths: Monster shot preventer, at 1.06 fewer points on 2 pointers, and .4 fewer points on 3 pointers. Opponents put up .62 fewer assists per game. Assignments average .1 fewer points per shot.

Nonstrengths: Slightly below average at stopping Free Throws, at .11 FT points per game above average. Average at Rebounds, Turnovers and Fouls.

Total Value: 1.75 points per game.

Kendrick Perkins

Strengths: Decent shot stopper, at .25 points on 2 pointers and .09 points on 3 pointers. Quality at stopping FTs, giving up .24 fewer per game. His assignments score .04 points less than average per shot. He is amazing at stopping rebounds, at .75 fewer per game.

Nonstrengths: Average with fouls and assists. Slightly below average at turnovers, forcing .11 fewer a game.

Total Value: 1.33 points per game.

Thoughts

The interesting thing is the ranking:

Allen 2.06
Rondo 1.98
Garnett 1.75
Pierce 1.52
Perkins 1.33

It should be noted that, of course, this doesn’t take into account the effect of Garnett and Perkins on the perimeter players. With helping bigs, all three can play much closer defense than they might normally do, which would allow them to dramatically lower their assignment’s shooting efficiency. All five players are within .7 points of each other - is this an indication of the inaccuracy of the method, that the effects of the good players on the defense are somehow aggregated? I say no. This is one of the best defenses in history, it stands to reason that each player be a substantial contributor. Surely, a good amount of the smalls’ shot prevention should be credited to the bigs - this isn’t a true indication of personal value. But it does tell us some things.

An interesting bit of data is how often opponents shot on each player. Both Allen and Rondo had their assignments take one less shot a game against them than normal. Perkins had opposing shots drop by .34. Pierce didn’t see his shots taken drop at all, but opposing PFs actually took .43 more shots per game than normal. It’s interesting that Rondo and Allen, who both were extremely effective at reducing shooting efficiency, had fewer shots against them, but Garnett, who was even better at shot defense, got an increase in shots against him. How weird is that?

It’s worth noting that this team does not prevent offensive rebounds particularly well (besides Perkins), nor do they force turnovers very well (besides Rondo.) What they do incredibly well, is shut down opponent shooting. Even Perkins, who is the weak link on this defense (though he’d likely be an anchor in another) slows down opposing shooters, and Garnett, Rondo and Allen are smothering.

The data put out isn’t ironclad, but it’s certainly interesting. :)

I have a lot of data here - who each player struggled against, dominated, how they fared against top tier competition, etc. I just didn’t want to vomit numbers everywhere and lose focus. If any further information would be helpful in any way, I probably have it somewhere, so let me know :)