Evaluating SF's Pitchers by RE24 Average

I've been giving a lot of thought to the whole question of who the Giants keep when Lopez meets Affeldt in the Thunderdome this winter (though the Mota vs Zito fight also looks like a good show).

While thinking about this, I came across the RE24 statistic for pitchers. It's a very useful measure that asks: "Given the 24 base/out states, how many runs did the pitcher save in the resulting play?"

I thought to myself: "There's got to be a way to use this number."

As fate would have it, there is, and it's brilliant.

The problem with ERA and relief pitchers is that it doesn't measure unearned runs. A relief pitcher typically inherits runners. As it is a relief pitcher's job is to get out of a sticky situations, it's nice to have a stat like RE24 that counts a run as a run and not as a free pass because you didn't let the runner on base.

There are other problems with ERA that are solved by RE24, like the fact ground ball pitchers have an advantage over strike out / fly out pitchers, but that's beyond the scope of my post (mostly).

What is needed, however, is a way to view a pitcher's RE24 as an average across 9 innings so that it can be compared to his ERA. In other words, we want to be able to look at the difference between a pitcher's earned runs an his total runs allowed. Finally, instead of using raw RE24, we want to use RE24 divided by the base/out leverage in order to get a context neutral number, since a pitcher coming in at the start of the inning faces significantly less pressure than a pitcher who comes in with one out and two on. Thus, it's a good thing RE24/boLI is an easy stat to look up.

As I explain in the comments: For pitchers, the deleveraged RE24 average (I need a TLA for that) ultimately tells us how well a pitcher prevents runs from scoring regardless of how those runners got on base

So how do we turn RE24/boLI into a 9 inning average for comparison to ERA?

I came across one Sabermetrician's happy little formula. It works as follows:

RE24 is measured as positive or negative deviations from MLB average, so to be able to directly compare it to ERA, we need to add back in the MLB-average runs. For Stephen Strasburg for example, multiply his innings pitched (18) times the league average runs per game, (4.28/9), then subtract his RE24 (3.52) to give a number (5.04) that’s directly comparable to his runs allowed (5). But this is on a scale of R/9 rather than ERA, so to convert it to an ERA scale I multiply by the MLB ratio of ERA to R/9 (3.94/4.28). Finally, we divide by Strasburg’s IP and multiply by 9, giving us an "RE24 average" of 2.32, which can be compared directly to his ERA of 2.00.

Feel free to let your eyes glaze over as I've done the hard part.

Let's see how the SF Giants relief pitching staff looks based on their neutralized RE24 average vs earned run average.

Name RA24 Average Earned Run Average
Sergio Romo 0.75 1.50
Santiago Casilla 2.10 1.74
Ramon Ramirez 2.34 2.62
Javier Lopez 2.36 2.72
Jeremy Affeldt 2.93 2.63
Brian Wilson 3.09 3.11
Guillermo Mota 3.46 3.81


Whoa! Wait, what???

Yes, you read that right. In a world where relief pitchers are judged not only by their ability to get their own batters out but to keep their inherited runners from scoring as well, suddenly  the way we feel about our bullpen in 2011 makes sense... the intuitive order of skill fits.

  1. Lopez beats Affeldt
  2. Mota beats Zito (more on that in a minute)
  3. Someone needs to pay Ramirez a bonus
  4. Romo executes a fatality


So do we have Zito handle middle relief or is he fifth starter material?

I've gone and tabulated the starting pitchers the same way in order to correct for ERA bias towards ground ball pitchers and include unearned runs. Here's how it comes out:


Name RA24 Average Earned Run Average
Matt Cain 2.37 2.88
Tim Lincecum 2.85 2.74
Madison Bumgarner 3.06 3.21
Ryan Vogelsong 3.13 2.71
Jonathan Sanchez 4.68 4.26
Barry Zito 4.89 5.87
Eric Surkamp 5.82 5.74


Feel free to discuss that too. The short version is (a) Matt Cain really was better than Tim Lincecum, (b) There was little real difference between Sanchez and Zito, and (c) There is a reason you always felt a little less comfortable watching Ryan Vogelsong than his ERA would indicate.

This FanPost is reader-generated, and it does not necessarily reflect the views of McCovey Chronicles. If the author uses filler to achieve the minimum word requirement, a moderator may edit the FanPost for his or her own amusement.

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