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— Where BTF's Members Investigate the Grand Old Game
Wednesday, January 29, 2003
Chris looks at catchers and DIPS.
In the 1999 Baseball Prospectus, Keith Woolner wrote what has become one the oft cited works regarding the value of a catcher and his ability to affect the game with his handling of pitchers. Woolner?s conclusion: "Looking at these results, though we would colloquially say that game-calling doesn?t exist, it?s more accurate to say that if there is a true game-calling ability, it lies below the threshold of detection."
It is a fantastic article and appeared to take a thorough approach to the problem and resolve it.
In 2000, a young unknown named Voros McCracken strolled into rec.sport.baseball and dropped a bomb called Defense-Independent Pitching Statistics (DIPS). The ensuing discussions were intense and thorough themselves. The theory behind DIPS is that, subtracting HRs, Ks, and BBs, a pitcher does not largely control the rate of hits on balls in play. Voros had done his homework, and he turned out to be right. DIPS made its way to BaseballStuff and then to Rob Neyer and Bill James. It was groundbreaking research, much like everyone thought of Woolner?s work the previous year.
You may say, what does one have to do with the other?
If the pitcher does not largely control hits on balls in play, then how can an analysis of catcher input that uses run values of balls in play be used? Let me be more clear: if the pitcher doesn?t control hits on balls in play, then analysis of a catcher?s game-calling ability cannot be related to hits on balls in play.
Woolner?s work, as near as I can tell, is interesting, but using the wrong data. The methodology is sound and should be used, but with a twist. In order to evaluate a catcher?s game-calling ability, one must study the only things that the battery does impact: HRs, Ks, and BBs.
I am not a mathemagician, so I?ll leave the Z-scores to someone like Voros or Keith.
Instead, I took all the pitcher-catcher pairs for 1999-2001 that faced approximately 200 batters in season N and N+1. I used Woolner?s study as a guide for that calculation. Keith did a great job of explaining what he did (although I still couldn?t understand it). Dan Szymborski explained I wouldn?t be able to use z-scores due to the way Keith used them for all hit events. I only have one hit event.
Ideally, one would take these pairs and calculate the catcher?s DIPS ERA for each, rather than using Pitching Runs. I started to do that, but in addition to not knowing Z-scores, I?m sort of lazy ? I?m just an idea man. I know someone will be right behind this article running the numbers, like Joe Dimino or Tangotiger, who are wizards with statistics and spreadsheets.
I calculated each battery?s HR/PA, K/PA, BB/PA rates and compared each to the same pitcher with a different catcher. I then subtracted the catcher?s rate by the "not catcher" rates to get a difference in the catcher and the "not catcher". I then ran correlations comparing season N with season N+1. If game-calling is an ability, the numbers should have a decent r and r^2 ? that is, if pitcher-catcher has a lower HR rate in season N and N+1, then it may be a skill that has this battery keeping the ball in the park. To be clear, I am not looking at a single catcher, but rather the set of 100 battery sets. If a pitcher-catcher has a higher HR rate in season N and N+1, that also counts.
My study reviewed all pitcher-catcher seasons that faced ~200 batters (Keith used 100 PAs). From those seasons, I generated 80 pairs of N/N+1 batteries.
The HR/PA and BB/PA is "catcher ? w/o catcher", while the K/PA is "w/o catcher - catcher". This is to keep negative numbers and positive numbers to always have the same meaning ? negative is good for the catcher, positive is bad.
Here you can see that Piazza?s relationship with Leiter, in 1999, resulted in fewer HRs, BBs and Ks. In 2000, his work behind the plate got Leiter more HRs, but fewer walks and more strikeouts. All of this is compared to the Mets? other catchers: Todd Pratt and Vance Wilson.
The correlations came up as follows:
All of these correlations are very weak to non-existent. This supports the idea that the catcher?s game-calling skills are not affecting the success of the pitcher.
After working this up, I also gathered all the data for catchers with and without pitchers. This data was treated in the same manner as the pitcher-catcher data, using the same pairs.
The correlations for the 80 battery sets were:
I knew what I thought, but I turned to smarter people for interpretation. After discussing with Ron Johnson, who knows regression, and a pass-by Mike Emeigh, the data seems to say the strikeout and walk rates show some significance in correlation, but the meaning here is the opposite of above. The K rate with a good R^2 indicates that the pitcher controls the rate, with no apparent effect from the catcher. The walk rate has good correlations and regressions indicate some impact from the catcher ? in the neighborhood of 10%. The relationship isn?t strong, but there does appear to be some effect. The HR rate still has no significant correlation -?pitcher or catcher in these data sets. This may not be enough data due to the few number of HRs allowed at all.
This DIPS-related look at catchers? effect on game-calling supports Woolner?s assertion that catchers do not largely impact the game with work behind the plate, running game excluded.
A more detailed study using an actual DIPS calculation may reveal more, including home/road statistics and ballpark effects. A larger group of battery sets would improve the ruggedness of the study.
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