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Monday, February 05, 2007
Defense Spectrum
Bill James popularized the Defense Spectrum. It’s one of those brilliant insightful ideas that is clear, concise, and obvious. It goes something like:
P-C-SS-2B-CF-3B-RF-LF-1B-DH
It has two specific meanings. The first is that the fielding premium is higher on the left-side than the right side. The second is as a player’s fielding abilities diminish, he gets shifted over to the right side.
How true is the second part?
For this particular blog entry, I’m going to modify the defense spectrum a bit, into:
P-C-IF-OF-1B-DH
where the 2B, SS, 3B are collapsed into IF, and the three outfield positions into OF.
Here’s a step-by-step as to what I did.
1. Look for all players with at least 150 IP (as pitcher) and 150 Games Played for non-pitchers, by the age of 23, and born after 1895. (Ruth was born in 1895)
Notes: Age is season minus birth year. I converted a catcher’s GP to 3*GP=G. I converted a pitcher’s IP to 1*IP=G. All other players: GP=G.
2. Figure the player’s primary position, through age 23.
Notes: Frank Thomas was the only player classified as a DH. He was dropped from the study. Billy Sullivan has no primary position (because of the way I treated the Catcher). They were the only two players born since Babe Ruth that didn’t survive the study.
3. For each player, figure how many GP at each age, starting from age 24.
4. Add up the number of games played grouped on the player’s primary primary position (from step 2) and age (from step 3).
You end up with this file which I have placed on Google Docs.
If we look at the first line, it says that all players classified as a pitcher by age 23 continued to be a pitcher through age 34. On age 35, 96% of all GP were as a pitcher, with 4% in the OF. (Johnny Cooney found life as an outfielder.)
And as the file shows, Bill James was right, and at a rather striking rate. The shift for the primary catchers was right along the spectrum as they aged. Infielders moved right along the spectrum as they aged (they didn’t play catcher or pitcher). Outfielders almost completely moved right along the spectrum toward 1B and DH, (with a few infielders along the way).
Firstbasemen moved to DH in their later years. However, while still in their 20s, a fair bit moved left, to the IF (3B mostly) or OF. If we look at 26-year old 1B, the guys that bucked the trend included among others:
- Chubby Dean: a 1B by age 21, he then became a pitcher
- Darin Erstad: one of the few that were obviously misclassified, as he played more games at 1B by the time he was 23 than any other position, because of the Angels situation
- Mike Ivie: he had some life as a 3B by the age of 23, and then played a little bit in the OF
- John Ellis: he has some life as a C by the age of 23, and then went back to catching for a while
There’s a total of 12 players in this exception group (including Jeff Bagwell who played one game in the OF), since Babe Ruth was born.
The interesting thing with this chart is that it can serve the basis for aging modeling. As an infielder gets older, we see that a few more players each year lose the necessary skills to remain in the IF, and become OF or 1B. As they move into easier competition fielding-wise, they are now compared against a tougher competition hitting-wise.
Next time, I’ll break up the three infield positions, and see how much movement, and the direction of movement, among 2B, SS, 3B.