Ranking NBA Championship Teams

The first thing to note is that just by looking at Basketball-Reference.com there are 62 factors that uniquely classify a team: MP FG FGA FG% 3P 3PA 3P% 2P 2PA 2P% FT FTA FT% ORB DRB TRB AST STL BLK TOV PF PTS OMP OFG OFGA OFG% O3P O3PA O3P% O2P O2PA O2P% OFT OFTA OFT% OORB ODRB OTRB OAST OSTL OBLK OTOV OPF OPTS PW PL MOV SOS SRS ORtg DRtg Pace FTr 3PAr eFG% TOV% ORB% FT/FGA eFG% TOV% DRB% FT/FGA, where OFGA indicates a given team’s opponent’s FGA per game average for a specific season.
The reason it is not meaningful to look at a specific statistic or a pair of statistics such as “three-point attempt rate” is that,

\boxed{\frac{62!}{2! 60!} = 1891} possible comparisons can be made.

Because of this, what is required is a detailed statistic learning approach. I looked at the full season statistics for the last twenty NBA champions from the 1995-1996 Chicago Bulls to the 2014-2015 Golden State Warriors.

I employed principle compoent analysis (PCA) to reduce the number of dimensions to see which variables contribute most to the variance of the data set. I found that the first 7 of 20 principle compoents explained 88.52% of the variance. Therefore, we can effectively reduce the dimension of the data set from 63 to 7.  This can be seen in the scree plot below:

A visualization of the 63-variable data set is as follows:

A matrix visualization of the full 63-variable data set.
A matrix visualization of the full 63-variable data set.
The power of principle components analysis reduced this high-dimensional dataset to a more manageable (but, perhaps still complicated) 7-dimensional data set, visualized as follows:

A visualization of the reduced-dimension dataset obtained via principle components analysis (PCA).
A visualization of the reduced-dimension dataset obtained via principle components analysis (PCA).
Next, I computed the Euclidean distance metric to perform hierarchical clustering on these seven principle components. I obtained the following result:

NBA Championship teams from 1996-2015
We notice immediately that:

  1. The 2015 Golden State Warriors were very similar to the 2014 San Antonio Spurs.
  2. Not surprisingly, Phil Jackson’s 2000 and 2002 Lakers teams were very similar to each other but not to any other championship team, and similarly for his 2009 and 2010 Lakers teams.
  3. Interestingly, the two teams that stand out which are truly dissimilar to any other championship team are the 2008 Boston Celtics and the 1998 Chicago Bulls.

This analysis also eliminates the notion that a team has to play a specific style, for example “modern-day play” to win a championship. In principle, there are many possible ways and styles that lead to a championship and an analysis such as this deeply probing the data shows this to be the case.

Some Thoughts On Howard Beck’s Bleacher Report Article

Howard Beck had an interesting article today on Bleacher Report, basically suggesting that the NBA finals, in particular, the current style of play embodied by The Golden State Warriors is somehow a vindication of D’Antoni’s basketball philosophies: “Shoot a lot of threes”, “Shoot in 7 seconds or less”, “Play small lineups”, etc…

While the Warriors have certainly embodied some of these philosophies, my personal opinion is that D’Antoni’s style of play can only be vindicated if there is a clear trend in championship teams that reflect these philosophies. As I show below, this is simply not the case.

I looked at the last 15 NBA Champions (from 2000-2014), and tried to see if there were any clear patterns in common between the teams. This is essentially what I found:

nbarankings15yrs

Two things that are immediately clear are:

1. There is very little that championship teams have in common!

2. The overwhelming thing that they do have in common is that 14 of the last 15 NBA champions have all been ranked in the Top 10 for Defensive Rating, something that Mike D’Antoni’s coaching philosophy has never really included throughout his years in Phoenix, New York, and Los Angeles.

This, I believe is the grand point that no one seems to be interested in making, perhaps, because according to the “mainstream”, defensive-oriented basketball, which, by definition is “less-flashy” still is the overwhelming common characteristic amongst championship-winning teams. 

Perhaps, the Warriors will win this year, but as I said above, I do not believe that one year is anywhere near enough to establish a trend and a vindication of D’Antoni’s basketball philosophies.

Further, there were some other things in Beck’s article that I found to be a bit concerning:

He claimed Today, coaches speak enthusiastically about “positionless” basketball—whereas 10 years ago, D’Antoni had to sell Marion and Stoudemire on the concept.”

This is not actually true. The triangle offense is the de facto example of “positionless” basketball, and has been around since the 1940s when Sam Barry introduced it at USC. Phil Jackson and Tex Winter’s Bulls and Lakers teams embodied the concept of positionless basketball. In fact, as can be seen from the diagram below (taken from http://khamel83.tripod.com/intro.htm), players don’t have set positions in the triangle offense. Rather, there are regions based on optimality and spacing:

triangle_spots357x350Many examples can be found from teams playing in the triangle offense system of guards posting up, big men coming out to shoot threes, etc…

The Effect of Kobe Bryant on The Lakers’ Play

Much has been said about the effect that Kobe has had on the Lakers this season. Byron Scott has been limiting his minutes at times, and at times has played him almost the entire game. There have been times this season where analysts and fans of the Lakers have claimed that the team actually plays better without Kobe. We decided to look at these ideas from a statistical perspective.

We looked at a whole bunch of data of Kobe’s play this season (courtesy of Basketball-Reference.com), and compared his individual play to whether the Lakers win games or not. This is what we found.

In this first classification tree, note that ‘Y’ denotes when the Lakers are expected to win, and ‘N’ denotes when they are expected to lose. What we found is any time that Kobe shoots at least 44.95%, the Lakers can be expected to win. If he shoots less than this percentage, then the only way the Lakers can win with Kobe still in the game is if he has less than 3 personal fouls, shoots less than 36.65% from the 3PFG% line and attempts more than 6-7 shots in the game.

From a statistical perspective, the Lakers can win many more games if Byron Scott optimizes the Lakers offense to get Kobe the ball in high-percentage shooting areas of the floor, i.e., closer to the basket than further away from it. Certainly, from a statistical perspective, Byron Scott’s way of allowing Kobe to play “freestyle” basketball is hurting the Lakers’ chances at winning games. 

kobeplot2

The second classification tree analysis that we did was to look at the whole debate over how many minutes is optimal for Kobe to play. What we found was that if Kobe plays less than 31 minutes in a game, the Lakers can expect to lose that game, while he is on the roster. If he plays more than 31 minutes, and has more than 7-8 assists, the Lakers can expect to win. The only other possibility for the Lakers to win games in this context is if he plays more than 31 minutes, has less than 7-8 assists, makes more than 6-7 of his shots, and plays less than 34-35 minutes a game.

Our previous analysis showed that the Lakers have the best chance of winning consistently when Kobe shoots a high percentage. This analysis shows that it is optimal for him to play between 31-35 minutes a game if he has less than 7 assists, but anytime he has more than 7 assists in a game, the Lakers can be expected to win. Therefore, from an offensive strategy perspective, the Lakers need to play more team-oriented basketball centered around Kobe. In hindsight, which is supported statistically, Kobe and the Lakers would be much better off in a post-oriented offense that promotes distributing the ball, high-percentage shots, and a slow pace. All of these three seem to be completely opposite to how Byron Scott has managed this team this year, and we feel that is why the Lakers have the record that they do!

kobeplot1