The Seventh Annual Sloan Sports Analytics conference is coming at the beginning of March (One of my nerd dreams is to attend) and the papers that are going to be presented at the conference have been posted online.
There are numerous interesting topics tackled ranging from Hockey, Baseball, Soccer, Tennis and Basketball, but the one that caught my attention today was a paper on NBA interior defense.
The paper by Kirk Goldsberry and Eric Weiss is titled “The Dwight Effect: A New Ensemble of Interior Defense Analytics for the NBA” and uses player tracking data to look at the efficiency of big men on defense.
To go about measuring this they take a two-pronged approach. The first is to measure how well a player defends the basket. This looks at the mix of shots (three pointers, mid-range, and close range) that occur when a defender is within five feet of the basket and efficiency of scoring. The second measure is what happens when a defender is in close proximity to the shooter. This is to determine the relative frequency that the defender is near a shot attempt and their effectiveness.
Here is where things get depressing for Warrior fans, the results of the case studies:
Overall more than 1/3rd of shots in our superset of 76,000 shots occurred with an interior defender within 5 feet of the basket. We assert that “dominant” interior defense can manifest in two ways: reducing the shooting efficiency of opponents, and also reducing the shooting frequency of opponents… We evaluated this by measuring the field goal percentage of close range shots when a qualifying interior defender was within 5 feet of the basket. Overall, NBA shooters make 49.7% of their field goal attempts when qualifying interior defender is within 5 feet of the basket… we found that Phoenix’s Luis Scola and Golden State’s David Lee were the worst defenders in these situations.
With Lee within 5 feet of the basket opponents shot 61% on close range shots, for compression sake that means that with Lee protecting the basket, opponents had the same close range scoring efficiency as Josh Smith. In the paper they included an image showing the shooting percentages from different close range shots for the best at this measure (Larry Sanders), league average and Lee.
That’s an awful lot of red.
But wait it only gets worse for Lee:
We also contend that dominant interior defenders often deter shots from even happening. Many NBA players will be reluctant to “challenge” a dominant interior player or be more likely to “settle” for a jump shot further from the basket. We evaluated this effect by examining the percentage of field goal attempts that occur near the basket when a qualifying interior defender is within 5 feet of the rim. We found that the most deterrent interior defender in this sense was Dwight Howard. Overall, when a qualifying defender is within 5 feet of the basket, the NBA shoots 57.2% of its attempts close to the basket; however, when Dwight Howard was the interior defender this number dropped to 48.2%. This is what we call the “Dwight Effect” – the most effective way to defend close range shots is to prevent them from even happening.
Lee definitely does not have many of these so called “invisible blocks” according to the data. With Lee protecting the basket, opponents seem to attack the rim more often. While the NBA average of close range shots is 57.2%, with Lee within five feet of the rim that number is 60.3%.
Let’s move to the second way of looking at measuring big man defense and how well a player defends shots when they are in close proximity to the shooter. To do this Goldsberry and Weiss looked at how often a player was within one, three, or five feet of a shooter and the field goal percentage on these shots.
Lee was slightly below average in the total number of shots defended, ranking 57th of the 93 qualifying big men. However when you look at the field goal percentage on those, again things are not pretty. Lee allowed shooters to make 53% of their shots when he was within five feet of them which was the third worst mark.
This isn’t really new information if you have watched the Warriors play. Lee is a very talented scorer and a liability on defense. These numbers confirm at least the second part of that statement. If the Warriors are to succeed it looks like it will hinge on Andrew Bogut taking the defensive pressure off of Lee who is not suited to be a defensive stopper.