A couple of weeks ago I wrote a piece featuring MarShon Brooks and the value of getting shots near the rim. One of the effects I highlighted, in addition to the greater expected effective field goal percentage, was the increased likelihood of getting offensive rebounds. Based on a Kirk Goldsberry's Court Vision Analytics visualization I spit balled the following table on expected offensive rebounds and estimated change in shot value compared to an estimated average of 32% offensive rebounds.
|Shot Location||HoopData FG%||Expected Offiensive
|Expected Marginal Shot
|Long Two (16-23)||38.30%||28%||-4%||36.83%|
I decided to follow up a bit looking at some data from NBA Wowy. Wowy doesn't have rebounds by shots location exactly but it does have them by prior shot type, which overlaps with shot location, using Mid two point jumpers, Lay Ups, Hooks, Tips, Free Throws and Three Pointers. Below, with a lot of copying and pasting, I put together Wowy's offensive and defensive rebounds last year for each team last year for those shot types.
The total percentage of offensive rebounds was 27.4% from the field, much lower than Goldsberry's 32% estimate, but matching the numbers from Basketball Reference. The percent of rebounds shot at the rim, using Lay Ups and Tips, comes out lower than my 'eye ball test' at 37.3% but the differential to the average is larger nearly a full ten percent.
It's interesting that Hook shots are so much lower in offensive rebounding percentage. It's tempting to attribute that to noise, given the relative rarity of hook shots these days at only three percent of rebound opportunities, but even with that there were over 3,000 rebounds of hook shot last year.
A hook shot is almost by definition one that has a defender between the offensive player and the basket (otherwise he would take a lay up or dunk) and nearly exclusively by big men who often get taken out of position by the hook motion. My shot location cluster analysis unsurprisingly found a connection between shooting from nearer the basket and getting offensive rebounds. And unlike driving lay up attempts there is much less likelihood to force help rotations from the defense, which puts the offense in much better positions to grab the rebound.
Those, of course, are factors teams will able to better quantify now that all of the teams have SportVu.
Below the fold offensive rebounds broken down by team:
The inclusion of rebounds off of free throws further lowers the offensive rebound rates compared to the Court Vision numbers. Also, looking at the shot types near the rim, lay ups and tip ins, the weighted average comes to 37% offensive rebounds compared to about 25% for both mid range twos and threes an even bigger discrepancy than the Court Vision visualization indicated.
Also, with Denver leading in offensive rebounds and San Antonio at the bottom there is not a strong correlation to offensive rebounding and winning, either way.