Rebounding Is Fundamental
Each time a player chooses to shoot the basketball, he is giving up possession of the ball in exchange for a chance to score points. If he does indeed score the points, he agrees that the other team will then have possessions so they can take their chance to score points. However, if the shot is not successful, the ball is live, and each player on the floor can go after the miss to secure a possession for his team.
Since each team has an equal number of players on the floor, capable of securing the rebound, is it safe to conclude that each team has an equal probability of getting the loose ball following a missed shot? Probably not. First, the shooter, 20 percent of his team is often at a disadvantage because his defender will usually be positioned between the shooter and the basket. In addition, the nature of defensive positioning, to stay between your opponent and the basket, probably provides the defensive team additional natural advantage when a rebound opportunity occurs
When I began collecting data for my efficiency project, one of the first issues I had to confront was the definition of a possession. There are two ways to go. First, one could define a possession as a single trip into offensive court without the opponent gaining possession. Thus, when the offensive team secures an offensive rebound, the possessions simply continues, with more than one opportunity to score on that possession. The second definition system is that each scoring opportunity [shot taken, free throw opportunity, or turn over] is a unique possession. Thus, when the offensive team secures an offensive rebound, it enjoys a bonus possession.
Some have selected the former definition [Jon Scott] and I chose the latter definition. I can see benefits in the Scott methodology in that the resulting offensive and defensive efficiencies are more readily comparable. However, the reason I selected the former method is that I felt it highlighted the important role that rebounding plays in a game. On a handful of games each year, the team that earns the higher offensive efficiency does not win because it allowed its opponents too many bonus possessions, a sufficient number to change the result.
Personally, I pay little attention to total rebounding numbers. When they are small, that means the teams shot the ball very well [fewer missed shots to rebound] and conversely, when they are large, that means the teams shot the ball poorly [more missed shots to rebound]. However, the proportion of rebounding opportunities that a team uses to secure bonus possessions are very important and often do affect the results of the game.
To this point, I have addressed this issue with a measure I have called “Offensive Rebounding Margin.” However, I do not necessarily have to have the rebounding statistics to arrive at this number because it is equal, algebraically to the difference in the total number of possessions in the game. However, this method of computation does not provide any information about how often a given team is successful in its quest for those important second chance scoring opportunities.
This season, I am expanding my data collection, and analysis, to examine the percentage of rebound opportunities that Kentucky , and Kentucky 's opponents convert their own missed shots into a bonus possession. [See TABLE I]
PERCENTAGE OF MISSED SHOTS CONVERTED
Through 4 games, it appears that this offensive rebounding rate may range between 25% and low to mid-40% range. What would be the NCAA D1 average? I don't know, but hope to explore the data for other teams over the course of this season and develop some sense about that value.
This is may be a better measure of a team's rebounding ability, proficiency, and aggressiveness. Consider a game in which both teams take 60 shots, with Team A making 25% and the Team B making 75%. There will be a total of 60 rebound opportunities; however, it does not follow that if B gets 32 rebounds while limiting Team A to 28 that Team B is the better rebounding team.
Based on the early data, lets assume that on average, a team will convert 1/3 of its misses into bonus possessions via offensive rebounds. Therefore, when Team A misses 45 shots, then Team A will get 15 offensive rebounds and Team B will get 30 defensive rebounds. Similarly, when Team B misses 15 shots, then Team B will get 5 offensive rebounds and Team A will get 10 defensive rebounds. This gives Team A 25 total rebounds and Team B 35 rebounds. Therefore, since Team A secure more, and Team B secured less than their average share of the rebounds, Team A is probably the more aggressive, and better rebounding team.
For the remainder of this season, and if the first year data appears worthy of further study, I will report for each game the percentage of available rebounds that Kentucky secures and allows as offensive rebounds for the game and for the season to date.
I welcome any comments and thoughts about these ideas.
Copyright 2005 Richard Cheeks