Relating Offensive Rebounds to Turnovers

I’ve been meaning to throw something together on this for awhile because it is a new and interesting way to look at things, I think. Through the traditional means of calculating possessions in basketball games an offensive rebound does not count as an extra possession, it is instead considered a continuation of a possession. I think some would contest that theory but like I did for CycloneFanatic.com a while back I ran a specific analysis where I considered an offensive rebound as a new possession. That column was simply to show how possessions are used for each Big 12 team at that time, found here.

What am I up to this time? Thinking through things logically when using the traditional formula to calculate possessions (FGA+TO-OREB+(0.475 x FTA)) there are just a few ways a possession can end for an offense; a made shot (free throw or field goal), a missed shot (free throw or field goal) with a defensive rebound, or a turnover. For this analysis I did not subtract offensive rebounds so that those offensive rebounds are counted as new possessions themselves.

What I’m driving at here is a specific relationship, the relationship between a team’s offensive rebounds and their turnovers. I am interested in this because these are the two ways an offense can either gain or lose a possession; with an offensive rebound they gain possession and with a turnover they lose a possession. This all gets back to the percentage of time that teams get a shot off on their possessions.

But what I’m really after is comparing offensive rebounding percentages and turnover percentages, primarily because a team like Iowa State while being 9th in offensive rebounding percentage is 4th in turnover percentage. A team may not be a great offensive rebounding team but if they excel at not turning the ball over then those things may be a wash. So the question is; which Big 12 team makes the most in both of those areas?

The quirk comes in with the fact that offensive rebounding percentage is calculated with no regard to possessions because a shot isn’t taken on every possession. By calculating possessions where offensive rebounds count as a new possession we can start to dive to the bottom of this. Here’s what I did: you can figure out the number of free throws that were “live misses” (misses that were live balls) pretty easily by taking a team’s total offensive rebounds added to the opponent’s defensive rebounds and then subtracting the missed two point and three point shots.

That is important because you can then calculate the percentage of possessions that were finished with a missed shot. Multiply the team’s fixed offensive rebounding rate by that number and you have a percentage of possessions where a new possession was gained.

The percentage of possessions with turnovers is easily done by dividing the turnovers over the possessions per game. What I then did was subtract the turnover percentage from the percentage of possessions gained via offensive rebounds to create a percentage margin of possessions created.

Put simply, I compared offensive rebounding percentage to turnover percentages to see which team does the best at creating (or not losing) possessions. Of course I couldn’t stop there and ran the same numbers for the opponents that each team has played. You can then compare the margin for a given team to their opponent’s margin for a net margin. Got it? Maybe?

All of the jibber jabber above is summarized by the below chart. It is sorted by the total margin column on the far right. The first three columns show all of the calculations for each team and the next three columns are the calculations for their opponents—where you of course want them to be negative in “creating” possessions when subtracting turnover percentage from offensive rebounding percentage.

The whole point was to dive in to the relationship between offensive rebounding and turnovers and those same numbers between a team and their given opponent. As it shook out, Oklahoma State and Kansas State are far and away the best team’s at “creating” possessions in the Big 12.

You’ll note that with their own possessions Iowa State is 4th in utilizing possessions but the fact that they force so few turnovers on defense and have struggled at times with rebounding percentage put them down at 6th for total net margin.

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