Friday, March 8, 2013

Minnesota and Rebounds: The Art of Cherry Picking

Last month, I looked at Bucknell and turnovers in college basketball strategy. Another interesting team in the 2013 season has been Tubby Smith's Minnesota team. The Golden Gophers rolled through non conference play, but are just 8-9 in the Big Ten. Despite the struggles, Minnesota is still 16th in efficiency in the country largely due to a ridiculous offensive rebounding percentage.

Minnesota ranks first in the OReb% by a wide margin and just 239th in DReb%. Offensive and defensive rebounding aren't exactly the same skill by any means, but it doesn't make sense that a team would be so far off in the two categories. Instead, I think that the large difference is more a product of the coach's system. Here are the two schematic possibilities for Minneosta's differential.

  1. Cherry picking - Minnesota is great at rebounding, but they decide to cherry pick (get out in transition) instead of having everyone defensive rebound.
  2. Allowing cherry picking - Minnesota is not quite as good at rebounding as their OReb% indicates, but they decide to crash the glass relentlessly on offense instead of worrying about transition defense.
The point here is that there is a natural trade-off between rebounding and transition plays.

To further examine this, I first looked at teams with the biggest differentials between offensive and defensive rebounding. To do this, I took the z-score of each, meaning I found how far away a team's OReb% and DReb% are away from the NCAA averages.

The 10 teams on the left are all Minnesota-like. They are much better at offensive rebounding than defensive rebounding. This means we would expect a much higher number of transition players per game than the teams on the right. The teams on the right are conservative when it comes to rebounding (notice Bucknell again). They get back on defense instead of going for offensive rebounds and box out instead of cherry picking. In both cases, the two strategies by the teams on the right limit plays in transition.

I decided to put this theory to the test using Using the data from that site, we can see how often these teams both go in transition on offense and allow transition plays on defense. I did this by looking at the percentage of times a team shoots in 10 seconds off missed shots versus the percentage of times a team shoots in 11-35 seconds into the shot clock off missed shots.

The table above illustrates the trade-off between cherry picking and transition. The teams on the left (the cherry pickers) are in transition 42% of the time and allow transition 41% of the time. The teams on the right (the conservatives) are only in transition 32% of the time and allow transition only 35% of the time. 

To me, three things particularly stick out about individual teams from the tables above:
  1. Minnesota is a weird team. It looks like the Golden Gophers are really just that good at offensive rebounding. I expected them to allow an extremely high percentage of transition plays due to crashing the boards, but it was actually the lowest of the top 10 teams at 36%.
  2. Northwestern St. is the biggest cherry picker in the country. I haven't watched film, but the stats show that Northwestern St. takes a shot within 10 seconds of getting a defensive rebound 58% of the time. This was by far the highest percentage and might be a reason why Northwestern St. is the second best team in the Southland.
  3. Bucknell ran a fast break once, just to see what it felt like. Yes, I think Bucknell is the most interesting team in the NCAA. Dave Paulsen's squad focuses on boxing out and holding teams to one shot. They only get out in transition on 14% of missed shots (not a typo).
For those of you statistically inclined, here are the scatter plots of the cherry pickers and non cherry pickers. You can see the r-squared values and how big of an outlier Minnesota is in all of this. Removing Minnesota increased correlation tremendously.

Cherry Pickers:


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