Measuring the Tigers Bullpen Woes

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 Ian Krol 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.  Krol gets more points in the first scenario because there was greater potential for run scoring.  Thus, Krol 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 RE24 for all American League teams is shown in Table 1 below.  The Tigers have an RE24 of -12.8 which says that their bullpen has cost them an estimated 13 runs compared to an average staff with the same number of outs. The interpretation is a little misleading because the average also includes starters.  However, all bullpens are compared to that same average, so the ranks are telling and only the Astros (-15.2) and Rangers (-16.8) have been worse than the Tigers.  

Table 1: RE24 for American League teams, June 13, 2014

Team	RE24
Athletics	35.3
Red Sox	29.2
Mariners	24.2
Orioles	13.7
Indians	7.1
White Sox	6.0
Royals	5.1
Blue Jays	4.1
Twins	0.8
Rays	-0.2
Angels	-2.6
Yankees	-6.0
Tigers	-12.8
Astros	-15.2
Rangers	-16.8

Data source: FanGraphs.com

The American League RE24 leaders among relievers are shown in Table 2 below.  New York Yankees right hander Dellin Betances leads the league with a RE24 of 13.2.  The Athletics have three pitchers in the top 15 - Fernando Abad (12.1), Dan Otero (9.1) and Sean Doolittle (8.4) - which is not surprising since Table 1 showed that their team RE24 is best in the league.   

Table 2: AL RE24 Leaders Among Relievers

Name	Team	RE24
Dellin Betances	Yankees	13.2
Koji Uehara	Red Sox	13.1
Zach Britton	Orioles	13.0
Fernando Abad	Athletics	12.1
Jake McGee	Rays	12.0
Burke Badenhop	Red Sox	11.7
Dustin McGowan	Blue Jays	9.9
Zach Putnam	White Sox	9.9
Wade Davis	Royals	9.9
Darren O'Day	Orioles	9.7
Aaron Loup	Blue Jays	9.6
Dan Otero	Athletics	9.1
Sean Doolittle	Athletics	8.4
Casey Fien	Twins	7.5
Adam Warren	Yankees	7.4

Data source: FanGraphs.com

Table 3 shows that right hander Al Alburquerque leads the Tigers with a 5.7 RE24 and that Joba Chamberlain (3.6) and Evan Reed (2.3) also have positive values, but none of them are close to being among the league leaders.  Closer Joe Nathan is one of the worst in the league at -8.0 which surprises nobody.     

Table 3: RE24 for Tigers Relievers

Name	RE24
Al Alburquerque	5.7
Joba Chamberlain	3.6
Evan Reed	2.3
Ian Krol	-1.6
Phil Coke	-3.7
Joe Nathan	-8.0

Data source: FanGraphs.com

So, does this mean that the bullpen is destroying the Tigers season?  Well, they are 29-4 when they lead after the sixth inning and this 88% rate is marginally better than the MLB average of 87%.  The Tigers have blown three leads when leading after the eighth and we can blame Nathan for that, but that's only one worse than the average team which has blown two games after the eighth.  

On the other hand, the Tigers are 2-6 when tied after six innings and the bullpen has to take some of the responsibility for that.  So, while the bullpen is not dooming the season as much as it may seem, it is certainly hurting the team and it's an area that needs to be addressed as the season progresses.