Wednesday, August 4, 2010

Update on Value of Blocked Shots

I do have an update on my research on the value of blocked shots. I made two preliminary rankings lists of the value of blocks by the leading blockers in the NBA between the 2006-2010 seasons. For the first list, I calculated points saved per block based on the shot location. I found that Brendan Haywood and Andris Biedrins (394 and 370 total blocks in 2006-2010, respectively) saved 0.987 and 0.982 points per block while Andrew Bogut (382), Chris Anderson (322), and Paul Millsap (319) saved 1.152, 1.130, and 1.131 points per block respectively, based solely on the location of the shot (so the value of blocking a running slam dunk is the same as that of a reverse layup in this model).

For the second list, I calculated points saved per block based on shot type. This is where I ran into problems, as although every shot is categorized with a specific shot type (no blanks or uncategorized shots), there are many idiosyncratic shot types such as running finger roll layups vs. driving finger roll layups. I've kept these for now (they should have negligible effect on the final values), and have not generalized the categorizations as of yet (say, into 3pts, dunks, layups, jump shots, etc.), but there is no question that dunks produce the most points per shot (PPS) of all the generic shot types, ranging from putback dunks at 1.81 PPS to running slam dunks at 1.97 PPS. Blocking dunks appears to be the most valuable skill for blocking any type of shot (all while earning a spot on Top 10 Plays on Sportscenter), while 'risky' jump shots such as the running jump, driving jump, and turnaround jump go down toward 1.06 PPS.


Anyway, more details for points saved per block based on shot type are to come, but Chris Anderson comes near the top again for the second model, saving 1.09 points per block based on shot type, while Andris Biedrins is near the bottom again, saving only 0.86 points per block based on shot type.

After fine-tuning both models of points saved per block (PSPB?) by shot location and PSPB by shot type, my plan is to compare them with a basic statistical report, then combine the two models, either with a straight up average or something to that effect. I'm also interested in looking at the results in a season-by-season format rather than all four seasons to see if blockers tend to retain their shot-blocking ability in certain shot locations or against certain shot types.

Hopefully, I can share some of my research with John Huizinga to see if our rankings agree. For now, I'll be searching for a way to combine shot location data with shot type data (the sample size becomes too small if I try to calculate PPS by shot location AND by shot type simultaneously), but I'll be sure to post a finalized rankings list as well as my complete methodology based on Ryan J. Parker's PBP data when I'm done.



That's why Chris Andersen is so valuable even though he is so ineffective on the offensive end.

porkbarbecueman said...

If you want to get really specific with some of this stuff, you might as well try to factor in how likely the defender is to foul the shooter when he goes for a block. I don't know if that's a function of the type of shot or the skill of the defender, but it seems like there are often times when a guy like Dwight Howard should probably lay off the block a little bit to avoid getting in foul trouble, since there always seems to be a little risk involved in even attempting to block the shot.

So if we could somehow get data on how many times Howard fouled the shooter when going for a block, that would also affect the "expected value" of a block attempt.

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