I have finally completed work on my visual NBA stat: Adjusted Defensive Impact by Court Location.1 I first explained how this stat works here, but in a nutshell this is a way to visualize how a player defends shots in the NBA adjusting for the other defenders on the court with him, the expected probability of the shot being made, and the other (non-shooting) offensive players on the court.2 This new model also adds the possibility of a team-wide effect that you might attribute to coaching (this is not visualized in any way just yet). I had many requests to also include something about how players affect the location of a shot. You can now see this at the bottom of each player’s chart. This is a simple regression that controls for defensive players only and shows you how a given player affects the volume of shots that are close (<8 feet), midrange, or 3 pointers. I have lots more to say below the jump but here's the widget, have fun poking around! Warm colors mean that opponents are more likely to hit a shot when the player is defending, cool colors mean opponents are less likely to hit their shots.
2013-2014 Adjusted Defensive Impact by Court Location
I’m going to keep the caveats pretty short this time, because I plan to have another post in the next couple of days that elaborates on things, but here are a couple of important notes on the whole project.
How did you make this? What’s new?
What this is not
This is not a holistic way of looking at defense. It only applies to plays where a shot was actually made. That means it misses plays that ended in a foul or a turnover. Drawing offensive fouls and creating turnovers can be a pretty big component of a player’s defensive game! A player could easily look bad by this measure and be a good defender nonetheless, because creating a turnover is a better defensive play3 than allowing the opposing team to take a shot (even a low percentage one). Moreover, each chart needs to be interpreted carefully. Take Jonas Valanciunas, for example. There’s a ton of orange and red on his chart. That seems bad but I would argue that there is a substantial silver lining for Valanciunas. As you can see, Valanciunas’s presence increases midrange shots by 4%. Those shots are easier to make when Valanciunas is on the court, but this may actually be preferable to a player who is good at defending the midrange but does not force shots there. This is simply because on average, a close shot is a much, much better shot than a midrange shot. So if you force shots to the midrange, that’s good, even if you allow those shots to go in at an above average rate. You would literally have to push FG% in the midrange up by 10-20% before a midrange shot would be better than a close shot.
Feel free to use this!