Table of Contents

Tuesday, October 02, 2007

2007 Fielding Data

I have updated my fielding translations to include final 2007 fielding data from THT.

There's been some confusion around the 'net about how these stats are calculated. I've gone into more detail elsewhere, but here's a quick summary of the methodology:
  1. First, for plays in zone:
    1. Determine, for each position, the average number of plays per ball in zone.
    2. For each player, determine their expected number of plays given how many balls in zone they experienced.
    3. Subtract the expected number of plays from the actual number of plays to get +/-plays in zone (+-Plays).
  2. Next, for plays out of zone:
    1. Determine, for each position, the average number of out of zone plays per ball in zone (it's not the best denominator, but it's better than innings--alternative suggestions welcome).
    2. For each player, determine their expected number of out of zone plays given how many balls in zone they experienced.
    3. Subtract the expected number of out of zone plays from the actual number of out of zone plays to get +-out of zone plays (+-OOZ).
  3. Sum together the +-in zone plays and +-out of zone plays to get +-total plays. I considered different weightings, but a 1:1 weighting seemed to be the best solution.
  4. Convert +-total plays to +-runs using the conversions published here by Chris Dial. If you're interested in why a play saved is typically worth roughly 0.8 runs, please refer to this recent post by Tom Tango.