tlongII
10-12-2009, 09:41 PM
http://mvn.com/bucksdiary/2009/10/the-hidden-value-of-joel-pryzbilla.html
Valuing those "extra" rebounds
In the next couple of days I'm going to rank the biggest Win Contributors at each position in the National Basketball Association last season. When I rank the center position, Joel Pryzbilla of the Portland Trailblazers will undoubtedly rank near the top of the list. I'll bet that comes as a surprise to most. Unless I totally misread the consensus opinion, I'd say Pryzbilla gets absolutely no respect at all.
In fact, when a writer on FoxSports.com recently ranked the Top 10 centers in the NBA, not only did Pryzbilla not make his list, I'll bet the guy didn't even consider Pryzbilla. But based on Pryzbilla's statistical production last season and the season before, the Minnesota big man should have been a shoe-in. Why wasn't he?
Overlooking the Big Rebounder
First, Pryzbilla has a very crude offensive game. Its very efficient, in that he converts the scoring possessions he uses into points at a high rate, but he will never be a high volume scorer or a graceful back-to-the-basket player. (Partly, I believe, because he spent only one season developing his game on the college ranks... but we'll never know)
The second reason I think Pryzbilla gets underrated is because he makes his greatest contribution in the rebound category, and specifically on the defensive boards. I guess fans undervalue defensive rebounding. I think that is because (1) they subconsciously believe tall men like Pryzbilla ought to be able to defensive rebound, so by doing so they aren't really doing anything special; and/or, (2) most fans believe that defensive rebounds grabbed by one player would likely have been grabbed by another player on the same team anyway, so again the player doing the actual grabbing is doing nothing really special.
But I think there is a way to identify the "extra" rebounds certain players like Pryzbilla produce, and to show how those rebounds can be converted into extra points "scored" for the player's team.
Applying Baseball's Defensive Zone Rating System
To help estimate the value of the contributions made by big time rebounders in terms of actual "points added", I turned to the logic behind baseball's defensive metric known as the "zone rating".
Baseball analysts use the zone rating to estimate the number of outs a fielder creates above or below the number of outs the average fielder would have created on the same number of chances. So, lets say 30 balls are hit into a third baseman's "zone", and he turns those 30 balls into 27 outs, whereas the average third baseman would have turned them into 21 outs. Baseball analysts estimate that third baseman created 6 outs that the team would not have gotten from an average third baseman. Of course, the rating is based on the assumption that a similar mix of batted balls are hit each fielder's way, but over time that assumption turns out to be pretty sound.
For my purposes here, rebounding in basketball is similar to fielding in baseball. Its often hard to tell which fielding plays (or rebounds grabbed) are ones anyone could have made (or grabbed), and which plays are ones that otherwise would not have had been made (or grabbed) but for the player involved. Because of that similarity, I decided maybe baseball's zone rating method... or something similar... could help estimate the value of the "extra" rebounds a player like Pryzbilla provides his team as compared to the number of rebounds the average player at his position would provide in the same number of chances.
But to do that I first had to calculate the % of defensive and offensive rebounds grabbed per opportunity by the average player at each of the five basketball positions. I was able to calculate those averages thanks to the precise defensive and offensive rebounding %s provided by 82games.com. Here are my results:
NBA Rebounding % averages by position
Defensive Offensive
PG: 8.3% 2.0%
SG: 8.7% 2.3%
SF: 12.1% 4.1%
PF: 16.8% 7.5%
C: 18.8% 9.0%
"Value" Rebounds: extra rebounds above average
By those figures, the average center would have converted 18.8% of the available opponent missed shots into defensive rebounds and 9.0% of his team's missed shots into offensive rebounds. Thus, by my logic, anything above or beyond % should be considered a "value" rebound... meaning, a rebound the team could not have expected to get from the average player at the position.
Converting Pryzbilla's Boardwork into added points
So how do Pryzbilla's conversion rates compare to the average center's? Very well. He had the best defensive rebound conversion rate among centers last season (29.0%), and his offensive conversion rate was above average as well (11.6%).
Using the baseball zone rating technique, Pryzbilla had 1766 opportunities last season for a defensive rebound, and he converted 512 of them, whereas the average center would have converted 332 of them. And Pryzbilla had 1753 opportunities for offensive rebounds and he converted 204 of those, whereas the average center would have converted only 158. So we can say that Pryzbilla provided 180 "extra" defensive rebounds and roughly 46 "extra" offensive rebounds.
Here's how I converted those numbers into "points added/saved". I simply assumed that every extra defensive rebound deprived Portland opponents of a possession they would have had if an average center were on the court, and every extra offensive rebound provided Portland with an extra possession they would not have had if an average center were on the court. I then used Portland's defensive efficiency average (103.0) to value each extra defensive rebound and Portland's offensive efficiency average (108.9) to value each extra defensive rebound.
Using simple multiplication, one could estimate that Pryzbilla's rebounding production on the defensive end deprived Portland opponents of approximately 185 points, and his rebounding production on the offensive end provided Portland with 50 points, for a grand total value added sum of 235 extra Trailblazer points.
If you use the very crude estimate that 35 extra points equals about one win, then you come up with roundabout six extra wins produced by Pryzbilla's rebounding alone. When put in that light, suddenly he doesn't seem like such a clod after all.
Valuing those "extra" rebounds
In the next couple of days I'm going to rank the biggest Win Contributors at each position in the National Basketball Association last season. When I rank the center position, Joel Pryzbilla of the Portland Trailblazers will undoubtedly rank near the top of the list. I'll bet that comes as a surprise to most. Unless I totally misread the consensus opinion, I'd say Pryzbilla gets absolutely no respect at all.
In fact, when a writer on FoxSports.com recently ranked the Top 10 centers in the NBA, not only did Pryzbilla not make his list, I'll bet the guy didn't even consider Pryzbilla. But based on Pryzbilla's statistical production last season and the season before, the Minnesota big man should have been a shoe-in. Why wasn't he?
Overlooking the Big Rebounder
First, Pryzbilla has a very crude offensive game. Its very efficient, in that he converts the scoring possessions he uses into points at a high rate, but he will never be a high volume scorer or a graceful back-to-the-basket player. (Partly, I believe, because he spent only one season developing his game on the college ranks... but we'll never know)
The second reason I think Pryzbilla gets underrated is because he makes his greatest contribution in the rebound category, and specifically on the defensive boards. I guess fans undervalue defensive rebounding. I think that is because (1) they subconsciously believe tall men like Pryzbilla ought to be able to defensive rebound, so by doing so they aren't really doing anything special; and/or, (2) most fans believe that defensive rebounds grabbed by one player would likely have been grabbed by another player on the same team anyway, so again the player doing the actual grabbing is doing nothing really special.
But I think there is a way to identify the "extra" rebounds certain players like Pryzbilla produce, and to show how those rebounds can be converted into extra points "scored" for the player's team.
Applying Baseball's Defensive Zone Rating System
To help estimate the value of the contributions made by big time rebounders in terms of actual "points added", I turned to the logic behind baseball's defensive metric known as the "zone rating".
Baseball analysts use the zone rating to estimate the number of outs a fielder creates above or below the number of outs the average fielder would have created on the same number of chances. So, lets say 30 balls are hit into a third baseman's "zone", and he turns those 30 balls into 27 outs, whereas the average third baseman would have turned them into 21 outs. Baseball analysts estimate that third baseman created 6 outs that the team would not have gotten from an average third baseman. Of course, the rating is based on the assumption that a similar mix of batted balls are hit each fielder's way, but over time that assumption turns out to be pretty sound.
For my purposes here, rebounding in basketball is similar to fielding in baseball. Its often hard to tell which fielding plays (or rebounds grabbed) are ones anyone could have made (or grabbed), and which plays are ones that otherwise would not have had been made (or grabbed) but for the player involved. Because of that similarity, I decided maybe baseball's zone rating method... or something similar... could help estimate the value of the "extra" rebounds a player like Pryzbilla provides his team as compared to the number of rebounds the average player at his position would provide in the same number of chances.
But to do that I first had to calculate the % of defensive and offensive rebounds grabbed per opportunity by the average player at each of the five basketball positions. I was able to calculate those averages thanks to the precise defensive and offensive rebounding %s provided by 82games.com. Here are my results:
NBA Rebounding % averages by position
Defensive Offensive
PG: 8.3% 2.0%
SG: 8.7% 2.3%
SF: 12.1% 4.1%
PF: 16.8% 7.5%
C: 18.8% 9.0%
"Value" Rebounds: extra rebounds above average
By those figures, the average center would have converted 18.8% of the available opponent missed shots into defensive rebounds and 9.0% of his team's missed shots into offensive rebounds. Thus, by my logic, anything above or beyond % should be considered a "value" rebound... meaning, a rebound the team could not have expected to get from the average player at the position.
Converting Pryzbilla's Boardwork into added points
So how do Pryzbilla's conversion rates compare to the average center's? Very well. He had the best defensive rebound conversion rate among centers last season (29.0%), and his offensive conversion rate was above average as well (11.6%).
Using the baseball zone rating technique, Pryzbilla had 1766 opportunities last season for a defensive rebound, and he converted 512 of them, whereas the average center would have converted 332 of them. And Pryzbilla had 1753 opportunities for offensive rebounds and he converted 204 of those, whereas the average center would have converted only 158. So we can say that Pryzbilla provided 180 "extra" defensive rebounds and roughly 46 "extra" offensive rebounds.
Here's how I converted those numbers into "points added/saved". I simply assumed that every extra defensive rebound deprived Portland opponents of a possession they would have had if an average center were on the court, and every extra offensive rebound provided Portland with an extra possession they would not have had if an average center were on the court. I then used Portland's defensive efficiency average (103.0) to value each extra defensive rebound and Portland's offensive efficiency average (108.9) to value each extra defensive rebound.
Using simple multiplication, one could estimate that Pryzbilla's rebounding production on the defensive end deprived Portland opponents of approximately 185 points, and his rebounding production on the offensive end provided Portland with 50 points, for a grand total value added sum of 235 extra Trailblazer points.
If you use the very crude estimate that 35 extra points equals about one win, then you come up with roundabout six extra wins produced by Pryzbilla's rebounding alone. When put in that light, suddenly he doesn't seem like such a clod after all.