During the course of the season, these run expectation differences get added and subtracted to the player's total and at the end of the season they get a cumulative total that shows how much better they've been than league average. Run expectation is extremely useful in generating linear weights which then can be applied to stats such as wOBA. However, many analysts agree that RE24 can be very useful in proving relief pitcher value because they often come in and leave in the middle of an inning. Say a starter loads the bases in the 7th inning and a reliever comes in and gives up a 3-run double and then a strikeout. All 3 runs get charged to the starter while the reliever gets a scoreless 1/3 of an inning. ERA doesn't properly show what happened, but RE24 does.
The table below shows the Tigers relievers' RE24 as of games played through 8/31 provided by FanGraphs:
| Player | IP | RE24 |
|---|---|---|
54 2/3
|
19.91
|
|
69
|
16.70
|
|
14 1/3
|
3.50
|
|
14 1/3
|
1.57
|
|
11 2/3
|
0.93
|
|
2
|
0.84
|
|
26
|
-0.11
|
|
18
|
-0.35
|
|
22 2/3
|
-2.18
|
|
19 1/3
|
-2.38
|
|
39
|
-3.27
|
|
33
|
-3.73
|
|
4
|
-4.78
|
|
4 2/3
|
-6.02
|
|
36
|
-6.46
|
|
4 1/3
|
-8.73
|
Tangotiger recently showed us how we can put RE24 on a RA9 or ERA scale:
If it helps, we can recast RE24 into an RA9 scale (i.e., similar to ERA) as follows. Say the league average is .48 runs per inning. Say you have a pitcher that has an RE24 of +40 runs and has pitched 200 innings. That means the league average is .48 x 200 = 96 runs, and our pitcher here is 40 runs better than that, or 56 runs allowed. So, his (RE24-based) RA9 is simply 56/200*9 = 2.52.So far there have been 16,965 runs allowed in 36,380 1/3 IP for a league run/inning of 0.47 so far in 2013. Using Joaquin Benoit as an example, he has pitched 54 2/3 innings; the league average would allow 0.47 * 54 2/3 = 25.49 runs. Benoit has been 19.91 runs better or (25.49-19.91) 5.58 runs. 5.58 divided by 54 2/3 times 9 = 0.92. The table below shows all of the Tigers relievers using this new metric (which I'm calling reRA9):
| Player | IP | reRA9 |
|---|---|---|
Rick Porcello
|
2
|
0.42
|
Joaquin Benoit
|
54 2/3
|
0.92
|
Jeremy Bonderman
|
14 1/3
|
2.00
|
Drew Smyly
|
69
|
2.02
|
Jose Veras
|
14 1/3
|
3.21
|
Jose Ortega
|
11 2/3
|
3.48
|
Bruce Rondon
|
26
|
4.23
|
Evan Reed
|
18
|
4.37
|
Al Alburquerque
|
39
|
4.95
|
Luke Putkonen
|
22 2/3
|
5.06
|
Darin Downs
|
33
|
5.21
|
Jose Valverde
|
19 1/3
|
5.30
|
Phil Coke
|
36
|
5.81
|
Jose Alvarez
|
4
|
14.95
|
Octavio Dotel
|
4 2/3
|
15.81
|
Brayan Villarreal
|
4 1/3
|
22.33
|
We could then compare the pitcher's reRA9 to his ERA to see if he's been overvalued or undervalued:
| Player | IP | reRA9 | ERA | Difference |
|---|---|---|---|---|
Octavio Dotel
|
4 2/3
|
15.81
|
13.50
|
2.31
|
Luke Putkonen
|
22 2/3
|
5.06
|
2.78
|
2.28
|
Brayan Villarreal
|
4 1/3
|
22.33
|
20.77
|
1.56
|
Evan Reed
|
18
|
4.37
|
3.00
|
1.37
|
Phil Coke
|
36
|
5.81
|
5.00
|
0.81
|
Bruce Rondon
|
26
|
4.23
|
3.81
|
0.43
|
Rick Porcello
|
2
|
0.42
|
0.00
|
0.42
|
Al Alburquerque
|
39
|
4.95
|
4.85
|
0.11
|
Jose Veras
|
14 1/3
|
3.21
|
3.14
|
0.07
|
Darin Downs
|
33
|
5.21
|
5.18
|
0.03
|
Drew Smyly
|
69
|
2.02
|
2.22
|
-0.20
|
Jose Valverde
|
19 1/3
|
5.30
|
5.59
|
-0.28
|
Jose Ortega
|
11 2/3
|
3.48
|
3.86
|
-0.38
|
Jeremy Bonderman
|
14 1/3
|
2.00
|
2.51
|
-0.51
|
Joaquin Benoit
|
54 2/3
|
0.92
|
1.48
|
-0.56
|
Jose Alvarez
|
4
|
14.95
|
15.75
|
-0.80
|
Villarreal and Valverde are no longer with us. Other pitchers like Dotel, Porcello and Alvarez have too small of a sample size to tell us much. It looks like Putkonen, who has a nice ERA, has been overvalued according to his RE24. And Benoit, who has been extremely good in his role this year, looks to be even better by looking at RE24.
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