Spoiler alert 1: Warning Jeff, stats article incoming.
Spoiler alert 2: In addition to having the best 1-on-1 perimeter defender in the NBA in Avery Bradley, the Celtics also sport the most impactful team defender in the NBA in Kevin Garnett. And if the numbers posted below are anywhere near the truth, Garnett isn't just the most impactful defender in the NBA this year. He's the most impactufl defender in the NBA this year by A LOT.
You know, business as usual.
But before I go too egg-head, let me take a minute to put this nerd-ism into context. This article will feature adjusted plus minus (APM). Many people, including a lot of people on here, aren't fans of APM because a) it isn't always easy to understand and b) it's still too "new" to have gained full public acceptance as really useful.
To address the second point in particular, I would point this out: over the past decade, there have been several analysts to come along and become the new voice for APM such as Dan Rosenbaum, Stephen Ilardi, or Wayne Winston. You know what happens right around the time they really establish their chops using APM? They get hired by an NBA team to do stats for them. Universally. The only way we as fans know that they've been hired is that their websites all of a sudden stop being updated publicly. For the last several years, the two biggest public sources for adjusted plus minus were Basketball Value and Jeremias Engelmann's site (regularized APM, or RAPM). For the 2012-13 season, mysteriously, both sites have stopped being updated publicly.
Moral to the story: we might not all understand adjusted plus minus, but the NBA does. And they absolutely devour people that get good at this stat. Which tells me that it must be pretty darn useful in player evaluation.
Now, to business. One of the reasons that I really appreciate the adjusted +/- stats is that this is the only statistical approach that we have to attempt to quantify defense. The box scores are woefully inadequate at this, and even the play-by-play approaches like Synergy have weaknesses because they focus more on 1-on-1 defense and not on global defensive impact. 1-on-1 defense is wonderful, as Bradley is helping to show us this season. However, defensive impact also includes help defense, rebounds, rotations, intimidation, communication...things that are difficult to put a check next to in a box score, and are even difficult to isolate in play-by-play approaches, but that can be truly appreciated when you look in depth at how much difficulty an opposing team has scoring the basketball.
I already mentioned that the two main APM sites stopped posting this year. Recognizing the void, the good folks over on the APBRmetrics board (for those unfamiliar, it's where NBA stat-heads go to hang out) decided to calculate and post the RAPM values for every player in the NBA up through the All Star break. The person that calculated these values said that this was still a work in progress so we shouldn't take it as gospel just yet. That said, this is the first adjusted +/- data that we've seen since Engelmann took down his 2013 data earlier this year. So without further ado, here are the top-10 big minutes defenders in the NBA in the 2012-13 season through the All Star Break according to defensive RAPM in this calculation:
And, you guessed it...
#1 Kevin Garnett (+8.1)
As a quick note of context, this data is for up through the All Star Break, which means that Bradley had only been fully healthy for about a month. Thus, the early part of the season when KG was pretty much a 1-man show on defense is heavily weighted in here.
The actual ranking of all 400+ players in the NBA for this study is found here. And as the person that calculated the stat pointed out, the absolute values of the stat could change as he modifies the calculation. So I would hold off on arguing that Garnett tops LeBron James for most impact in the NBA, as that ranking suggests. In fact, the author says it better, "(W)hen you see KG and Amir (Johnson) ridiculously high on D you should assume the number is too high, but that they're pretty excellent." So take the overall rankings with a grain of salt. However, even if the absolute number changes for defense, the relative ranking should stay about the same. In other words, KG's defense might not measure out as more impactful than LeBron's offense once the smoke clears...but he still grades out as the most impactful defender in the NBA...by a lot...yet again.
And when you combine KG's global defensive impact with Bradley's on-ball brilliance, then sprinkle in strong perormances from the Captain and Courtney Lee with a few OMG blocks from Jeff Green for good measure...suddenly you have a defense that's EXTREMELY dangerous, especially in the postseason. The Heat (and everyone else) better watch out...