ezPM v.2.0: Incorporating Counterpart Defense or "The Biggie"

J.D., in the current version of the metric counterpart turnovers are split 50/50 between a player and his teammates. In other words, Ibaka would get half the credit for his counterpart turnovers, while the other half gets split among his teammates. As for charges, from the few stats that I have seen, the league leader in drawing charges is usually around 1 per game, sometime less. It would be really nice to give that guy credit. Unfortunately, like I said, there's nothing I can do about it without the data.

The problem is that who draws the charge is not listed in the PBP data. Without that, I have no way to credit anyone, unfortunately.

Hi, J.D. I actually don't double count the missed shot and the block. In an earlier version I did, but I quickly realized it and modified the code. To your second point, 82 games did a study a while back on rebounds on blocked shots. I believe the average is around 57%. Here's the link: http://www.82games.com/comm16.htm

We can all come up with scenarios where something looks good or bad depending on the context. It seems clear to me that, on average, a poorer defender will more often give up easier shots or allow cleaner (less harried/hurried) passes to be made by his counterpart, while a better defender will generally prevent those shots/passes. Perhaps, I should do a quick post simply looking at counterpart assist ratios, to see if the rankings match what I might expect, or whether it is more random or even inversely correlated, which I suspect is what you would expect.

Uh, yes. :) See... http://thecity2.com/2010/12/28/ezpm-1-0-now-with-play-by-play-data/#comment-238

Thanks, Daniel. Yeah, the "tuning" is how I'd like to proceed. Do you think it would be crazy to do this tuning at the team level? Each team has different defensive schemes, and it might not be right to have one function across the whole league. Just a thought. It would be a ton of work obviously, so maybe not a first pass kind of thing.

I don't know about that... you could try it, but I suspect it would be subject to a bunch of random error and would have to be regressed a bunch. One way to attack it would be to assign credit based on position--e.g. post defenders get more of the credit for a PG scoring against them than does the 2G. Much exploration on this would be required. p.s. You ever going to release your parsing code? :-)

When switching, would you say that most of the time the difference in position was +/- 1?

I haven't tracked that. My first guess that it would be more due to small / big pick n' rolls, baseline screens, rotating out to a 3 point shooter, etc. and because 2s & 3s and 4s & 5s tend to be on opposite sides of the court.

A drive that beats a perimeter man ends up with a help defense response (a kind of switch) often from a big. I'd guess that the average defender position number change in a switch of any kind is closer to 2 than 1 . Probably higher when the position rank goes up (on more drives inside), probably lower when it goes down (more likely perimeter shots). Maybe you could model switching and estimate the shares of credit and blame to other positions a bit better than even shares but it would probably be worth another video test before committing to it.

Yes, once you have a complete metric with shot defense divided "fairly" (in the sense of being based on only those minutes a player is actually on the court and not team level shot defense for all minutes) , then you have a much better "statistical" measure to compare to player Adjusted +/- and the other things you mention.

The shot defense was also previously based on "those minutes a player is actually on the court". It sounds like maybe you weren't aware of that?

Sorry, the criticism of 'team level shot defense for all minutes, not when actually on the court' was in reference to some other metrics, not yours. I thought that would be clear, but I guess I should have specified further. And of course many metrics have had no shot defense at all.

Crow, I know you're not suggesting that Andrew Bogut and Dwight Howard are not "step up help" defenders. They are atop the charts of any defensive basketball metric, and they don't take hits when counterpart scoring or assists modify the rating -- in fact, they improve when blame for assists are entered into the equation. So why does Noah, who plays the same position and is considered by many a top defender, take such a hit? The simple answer is that Bogut and Howard are better on-ball defenders than Noah, and they've got higher defensive rebounding rates as well. Bogut and Howard give help, but they're more experienced and smarter about giving help (Not "overhelping"); they're certainly blocking more shots, cutting off weak-side rebounding; and, in general, they're not losing track of their man on the offensive glass. To the eye, Noah looks good and very active, but he gets beat often in the post, and roams and overcommits to help. He does look like he's working harder than Howard and Bogut, and plays with a lot energy, but a lot of that is wasted activity. 4th year pro, still learning.

I agree that your comments. Noah is not at the same level as Bogut as a 1 on 1 shot defender this season and Howard is even better. Noah isn't as good this season 1 on 1 as Thomas or Asik either. He is a better rebounder than Thomas. Help defense impact of the Bulls centers might be hard to call accurately. Asik has a very strong team defensive efficiency while on. Regular Adjusted +/- also calls Asik the best of the 3 as a defender by a significant margin. I agree that Noah's reputation is better than what he did this season, coming off injury. But he was probably better before, or at least a lot better than his old teammates under the old coach.

Agreed, I've been very impressed with Asik this season, and Kurt Thomas is very solid. Noah is overrated as a defender. The hand is no excuse -- Bogut played with one arm all season and was still a force defensively. I'm a Bucks blogger, and, as such, because we are one of the few teams where our center is the franchise, I pay close attention to center play. This season, Bogut blocked more shtos than Howard, but that's because he's challenged more often than Dwight. Both players stay at home defensively, and Bogut has learned -- and has said -- that he doesn't leave the floor until the opponent leaves his feet. It's a subtle thing - the ball fakes don't work on those guys -- they are waiting until offensive players actually leave their feet and shoot before they go up for the block. And they wait to give help until the last instant. It's an expericnce thing, I believe. That's just one aspect of it. On the ball, they don't even look like they're working hard in the post -- they stay down, use their physical size to maintain position. And they don't lose contact with their man. Bogut's thing is to hit the player he's guarding in the chest all game long. He's constantly tapping the opposing center with his hand to keep track of him, to know where he is. It's a great way to play off-the ball defense. The metrics agree across the board -- Howard and Bogut aren't just a little better than the big men of the league, they're a lot better -- in a league of their own. The question here is -- how the heck does Ronnie Brewer outscore their impact? I know he leads the Bulls in steals, but one would think it impossible for a wing player to outscore Dwight and Bogues as far as defensive impact. Can't wait for the next Bulls playoff game to see what he's doing out there.

Ronnie Brewer is an interesting case. In fact, it is not just ezpm that his defense rated highly. 1-yr defensive RAPM is +3.1, which would be one of the league leaders. In addition to steals, his counterpart on the opposing team likely racks up fewer assists and shoots with lower efficiency. If it were purely a function of team defense, one would expect Bogans to rate similarly. Having said that, I certainly don't believe that Brewer has greater defensive impact than Bogut or Howard (or Garnett or Duncan, etc), so it is an interesting case. I tend to think the numbers are meaningful in the sense that they give us an idea that he's a better than average defender at his position, but you can only get so much out of looking at counterpart data. There are always going to be statistical outliers, and maybe Brewer is an example of that.