Monday, May 14, 2007
Replacement-Level Fielding
How good or bad is the fielding of the bench players compared to the starters? This is what I did:
1. For each season from 2000-2006,
2. Select the 30 players at each position that played the most and classify them as “Starters”
3. Figure out the putouts and assists per 9 inning of the Starters at each position
4. Take the rest of the players and treat them as “Bench”
5. Do the same as #3 for these players
6. Compare
From 2000-2006, the average SS Starter had 2.96 assists per 9 inning game (27 outs), while the Bench SS had 2.92. Here’s how each position group did:
Catcher: Starters, 0.48 assists per game, Bench, same
SS: 2.96, 2.92
2B: 2.93, 2.91
3B: 1.99, 1.93
1B: 0.67, 0.65
Putouts
CF: 2.57, 2.58
RF: 2.05, 2.07
LF: 1.94, 1.95
In short, the typical starting infielder is about +.04 plays per 27 outs (5 runs per 162 GP) better than his backups, while the typical starting outfielder is about -.01 play (1 run per 162 GP) worse than his backups.
For all intents and purposes, the fielding performance of backups are roughly the same as the starters.
Any chance that the pool of pitchers for starters and backups are different in terms of GB/FB% (since backups tend to come into games late in the game, when short relievers are in who get more K’s)?
How about day versus night games being different in terms of putout and assist rate (since backups tend to play in day games following night games)?
And of course, some percentage of backups are defensive replacements late in a game, so while backups could be overall the same as regulars, it could be that the true replacement defender is worse than a regular but that these late-inning defensive replacements bring up the whole pool of backups. So it depends on what you are trying to determine and what your definition of replacement defense is.
Tom, if you send me your list of backups and regulars or give me your definition, I can compare UZR.