Rim Protection COMStat (lots of numbers)
(Update 12/29/13 - Updated numbers and such here)
(Update 1/13/14 - posted google doc with current numbers here)
(Update 1/24/14 - posted google doc with updated numbers for entire league here, explanatory post here)
(Update 1/27/14 - with help from Backboard Blues, updated with individual contest%'s here, google doc here)
However, I don't think we have data that really speaks to "shot prevention" on an individual basis. We can look at opponent's shot locations to tell us some things, but is preventing a shot at the rim by completely not covering the perimeter really shot prevention in a meaningful sense? For a good shooter, an uncontested midrange shot is a 55% shot, whereas a contested paint shot is roughly 50%, and that's best case scenario, forcing a "dead zone" shot. An uncontested corner 3 for a good shooter is roughly equivalent to an uncontested short range shot in terms of value. So "preventing" shots in the paint might cost more than it's worth.
For this reason, I'm going to look at rim protection completely in a vacuum. The following number crunching is not intended to speak to any other part of defense, and I tend to think that players playing the 4 are more likely to be hurting their team by protecting the rim than centers, given the prevalence of "stretch 4s" around the league. It also does not take into account the fact that some teams might give their bigs more or less of an "opportunity" to protect the rim by allowing or preventing penetration. This data compiled by Lindell (thanks again) sheds some light on those matters.
Opponents are shooting roughly 40% at the rim on shots Hibbert contests. Considering leaguewide shots at the rim are scored at around 60% and uncontested shots at the rim are scored at around 75%, this sounds amazing. Hibbert alone is saving the Pacers over 2/3rds of a point on every shot he contests! However, an "average" (see below) NBA big "holds" opponents to .499% on these shots. Suddenly, when compared to the average big, Hibbert is preventing a more prosaic .2 pts per shot.
He remains incredibly impressive because of another stat entirely: his number of contests per game. Hibbert is currently tied for 7th in number of contests per game at 9.6 per. In my opinion, this statistic is almost as important if not more than opponent's FG%. The difference between Hibbert and the "worst" rim defender in this sample is 20.7% or about .41 points per shot. The difference between an average big man and an uncontested shot at the rim is about 25% or .5 points per shot. Just being large and there turns out to be pretty useful!
So players have rim protection value in terms of both quality and quantity of shots contested, and I fired up the old spreadsheet to see what we could see in terms of meaningful comparisons. Below are my first pass at ranking NBA bigs based on "points prevented above average" through rim protection on a per game, per 36 and season total basis. (See note at the bottom for a summary of the methodology).
- I strongly doubt Chris Kaman maintains his spot, though he in limited action has "held" opponents to the lowest FG% on shots at the rim on a large number of attempts/36.
- Neither Love nor Pekovic show up very well
- Other surprising players who appear "negative" in this analysis are Al Horford, Anthony Davis and especially Marc Gasol. Horford and Davis are at least explicable based on them spending more time away from the basket (and given Davis's shot blocking ability there is undoubtedly some deterrence/prevention lowering his number of contests). I have no good explanation off the top of my head why Gasol shows up poorly though. Memphis does play at a slower pace and allows fewer rim attempts than most teams, but his standing is still surprising.
- Miles Plumlee does well, Markieff Morris, not so much
- for this data, I used SportVu info all NBA players who have played at least 5 games and contested at least 5 shots at the rim per game, which gave me 63 players, so about 2 per team, more or less overlapping with the starting big men in the league.
- When I'm talking about net value, I'm talking about value above or below the average of this sample rather than replacement level because replacement level is extremely tricky, and I have a hard time believing that any player who made his way into this sample actually provides negative rim protection value.
- To find the raw "points prevented" I assumed an opponents FG% of .750 and subtracted the points scored on
- The above/below average analysis is based on the sample average big man preventing just under 4.5 points/36 by contesting 8.91 FGA/36 at a .499FG%.
- The numbers are NOT pace adjusted.