Sunday, July 22, 2012

Rankings Now Adjusted for Ballpark

In this post on ball park adjustments, I derived how the betting markets adjust moneylines and run totals to account for where the game is being played.  From that analysis, I found that home field advantage is relatively constant across teams (it's worth about a 0.4 run advantage).  In contrast, I found that the betting run total shows significant variation from ballpark to ballpark.  As it is common knowledge that some parks are hitter friendly (e.g. Rangers Stadium) and some are pitcher friendly (e.g. Petco Park), it's not surprising that the betting market has factored that knowledge in.

The purpose of this post is to announce that the team rankings and pitcher rankings, as well as The Ticker features of this site, now account for these ballpark adjustments. You can find the adjustments themselves here.  I have based them on an average of the 2009-2011 seasons.  Here is an explanation of the fields:

  • Home - How much the betting market adds/subtracts to the expected home team's run total
  • Away - How much the betting market subtracts/adds from the expected visiting team's total
  • Home Field - This is the home field advantage, in runs.  It is just the difference between the home and visitor column
  • Total - How many more (or less) total runs are expected to be scored per game, relative to the league average.  It is just the sum of the home and visitor column
The impact of this change did not move the overall rankings much.  The impact really shows up in the offense, defense, and pitcher rankings.  The rankings are now on a "field-neutral" basis and reflect the betting market's evaluation of team and pitcher strength prior to the ballpark adjustment.

As expected, Felix Hernandez dropped somewhat in the rankings as the fact that he starts half of his games in pitcher-friendly Safeco Park is now effectively being pulled out of his RAA metric (Runs Above Average).

The Rockies' defense/pitching, however,  is still dead last in the league (0.77 runs below average), even after factoring in the Coors Field ballpark adjustment of 0.88 runs.

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