Sunday, May 27, 2012

Using RE24 to Evaluate Relievers

In a recent post, I used the RE24 statistic to measure batting contribution including situational hitting.  The statistic is appealing because it gives batters more credit for hits with runners on base than for hits with the bases empty.  This concept can also be applied to pitchers, relievers in particular.

Statistical evaluation of relievers is difficult for a couple of reasons:
  1. They pitch so few innings that their statistics can be influenced heavily by a couple of really bad outings.
  2. Their actual value depends on game situations more than any other player (this problem will be addressed here)
Using ERA to evaluate relievers is problematic because relievers often make appearances with runners on base and give up other pitcher's runs. So a pitcher could have a low ERA without actually being that effective. FIP ERA which is based on walks, strikeouts and home runs allowed rather than runs allowed is better but it still does not consider the game environments in which a reliever pitched.

The RE24 metric estimates the number of runs a pitcher saved or cost his team based on his numbers of singles, doubles and all other events allowed including outs.  It also considers the situations in which these events happened.  For example, if Tigers southpaw Phil Coke enters a game with two men on base and nobody out and retires the side he will get more credit than if he comes in with the bases empty.  Coke gets more points in the first scenario because there was greater potential for run scoring.  Thus, Coke saves the Tigers more runs if he frequently pitches well with runners on base than if he always starts an appearance with the bases empty.

The American League RE24 leaders among relievers are shown in Table 1 below.  Oakland Athletics right hander Ryan Cook leads the league with a RE24 of 11.87.  This means that he has saved the Athletics an estimated 12 runs compared to an average pitcher with the same number of outs. This is not too surprising since his ERA is 0.00. 

Table 1: AL RE24 Leaders Among Relievers

Pitcher
Team
RE24
Cook
Oak
11.87
Ogando
Tex
11.05
Atchison
Bos
10.44
Strop
Bal
9.63
Ross
Tex
8.97
Wade
NY
8.68
Johnson
Bal
8.29
Uehara
Tex
8.16
Duensing
Min
8.06
Pestano
Cle
7.70
 Data source: FanGraphs.com

There are no Tigers in the top ten, but lefty Duane Below is 16th in the AL at 6.12.  Other Tigers relievers with 10 or more innings are listed in Table 2.  Below, Joaquin Benoit, Octavio Dotel and Phil Coke have all saved the team runs and Jose Valverde has been league average.  The now departed Colin Balester cost the the team an estimated 6 runs.  

Table 2: RE24 for Tigers Relievers

Pitcher
RE24
Below
6.12
Benoit
3.95
Dotel
3.77
Coke
1.20
Valverde
0.01
Balester
-6.23
Data source: FanGraphs.com

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