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Where the (Defensive) Rebounds Are

One of the trends I've mentioned in recent DSS charting posts is the surprisingly low success that the Kentucky Wildcats have had when grabbing the numerous missed shots they create. In conference play, the Cats are grabbing 66.6% of opponents' missed shots (per KenPom). That mark ranks 6th in the SEC and would be tied for 216th in the nation. In all games, Kentucky is grabbing 69% of available defensive rebounds, good for 117th in the country.

The fact that UK has been better overall than they have been in conference play indicates that they were doing much better before conference play began. That's not surprising given the respective level of competition between the conference and non-conference schedules, but UK faced a number of excellent offensive rebounding teams in November and December including North Carolina (6th in the nation in OR%), Loyola MD (12th), Old Dominion (16th), and Lamar (21st), and Louisville (38th). It's not like they beat up on patsies in this particular area.

Indeed, when Kentucky entered conference play they were allowing teams to grab 31% of their own misses against a set of opponents who were otherwise grabbing 35.1% in their other games. The most common explanation is that as a shot blocking team, Kentucky often sees their best rebounders out of position as a result of attempts to block shots. I think that's likely part of it, but I'm not convinced it's the whole story.

For the Vanderbilt game, I decided to keep track of where rebounds came from, based on the location of the missed shot that created the opportunity. I marked down whether Kentucky or Vanderbilt grabbed the rebound and whether it was a player rebound or a team rebound (more on that in a second). The results are in picture form below.

Before we get to the rebound location, here's some background as to how rebounds are credited. They are divided into 3 categories, of which only 2 are relevant to the conversation.

  • Player Rebounds: exactly what you expect, rebounds grabbed by a player.
  • Team Rebounds: these are rebounds that occur because the ball goes out of bounds before it's controlled by a player, such as on airballs, blocked shots, or just being knocked out of bounds by someone going for the ball.
  • Deadball Rebounds: These are entirely an accounting trick, based on the idea that every missed shot and free throw should generate a rebound. These are rebounds that no team has the chance to get and occur most frequently on a missed free throw where another attempt is forthcoming or when a non-shooting foul occurs while a shot is in the air (such as over-the-back).

Team rebounds might or might not show up in a box score depending on where you look. They do show up in the ones available on UKathletics.com and are included in determining Offensive and Defensive Rebound%. Deadball rebounds are rarely included in a box score, although they are listed at UKathletics.com. They are not included in the Rebound% calculations and so I am not concerned with them.

Dreboundsvandy_medium


  • I missed a 3 point attempt somewhere as well as a 2 point attempt that were rebounded by Vanderbilt players, so there are two offensive rebounds missing.
  • Most of the Commodores' rebounds came on close shots inside, lending some credence to the block attempt theory. It's worth noting that in the second half UK did not collapse inside as much as they did in the first half and they also were much better at grabbing misses in that half.
  • The sequence that sticks in the mind comes from the first 3 possessions in the game. Terrence Jones helped off Lance Goulbourne to help when the ball went inside to Ezeli, and Goulbourne grabbed the offensive rebound all 3 times.
  • As you can tell, the vast majority of Vanderbilt's inside shots came from the right side. I think this is interesting although I'm not sure it has any bearing on rebounding the ball.
  • When Kentucky blocked a shot, they got the subsequent rebound 5 times out of 12.

I initially tried to keep track of offensive rebounds that occurred because of help defense leaving the eventual rebounder, but that proved to be too much to do along with everything else I was trying to keep track of. So I'm afraid I don't have anything stronger to say about that theory right now. The combination of the results on blocks and the good job the Cats did rebounding after long jump shots are certainly in favor of the block theory.

In hindsight, it might have been more useful to keep track of where the rebounds were grabbed instead of where the shots were taken. In the end this may not matter much. In this game, Vanderbilt scored 15 points on 14 possessions where they grabbed an offensive rebound (they had some possessions with multiple offensive rebounds) for an efficiency of 107.1. That's not much different from their overall efficiency of 103.3 in that game. One game is hardly conclusive, but maybe good defensive rebounding is overrated in this instance? That would be a really counter-intuitive conclusion, but it might be interesting to explore further.