Wednesday, September 17, 2008
Batting Runs Above Average Using Run Expectancy
My post about contextualizing linear weights got linked over at The Book Blog, which led to a new discovery for me. Fangraphs, which is really a wonderful site for stat dorks, tracks a version of batting runs above average that is not context-neutral. Instead, they use the difference in run expectancy before and after every plate appearance or batters faced. The full glossary definition is here, but here’s the heart of it.
BRAA (batting runs above average): BRAA is the difference in run expectancy (RE) between the start of the play and the end of the play. That difference is then credited/debited to the batter and the pitcher.
What I like about this is it adds the out state to the base states I was using, and it includes pitchers, and it doesn’t give different weights based on innings or scores. Basically, you look at what an average player adds to his team on each specific play for each of the 24 base/out states, then you compare that to what each player actually does.
Since it includes pitchers we can do direct comparisons of everyone on the team and see how they’ve stacked up this year as well.
Here’s the offense.
Here are the starting pitchers.
Here are the relievers.
And here’s everyone.
These numbers are not position-adjusted, so you may want to account for that. Here are my 2008 AL position adjustments based on 650 PAs.
C 10
1B -5
2B 0
3B 0
SS 12
LF -4
CF -3
RF -6
DH -6
So you’d subtract around 5 runs from Giambi’s value, you’d add around 12 to Jeter’s (pro-rated). Here’s how the overall chart looks if we position-adjust for the offensive players.
These numbers are against average, not replacement level. Also as a reminder, a measure like this is not necessarily supposed to be predictive, it’s retroactive.
This says that in total, the Yankees have been about four wins better than average including everything except baserunning and defense, although I think the bulk of defense is included in the pitchers’ BRAA. An average team over 151 games would be 76-75 or so, and the Yankees are 80-71, or four games better than average.
Update(s):
As requested by DaPuj, I’ve added the context neutral batting runs above average for the position players to the overall Yankee chart.
And here’s the top 25 in the AL for contextualized, position adjusted BRAA for position players.
And the bottom 25.
Lastly, adding in pitchers here’s the top 50.
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