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BP: Deserved Run Average


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http://www.baseballprospectus.com/article.php?articleid=26195

So, as an overview, here is what DRA does, step by step:

Step 1: Compile the individual value of all baseball batting events in a season.

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Step 2: Adjust each batting event for its context.

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Step 3: Account for base-stealing activity.

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Step 4: Account for Passed Balls / Wild Pitches.

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Step 5: Calculate DRA (Deserved Run Average).

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http://www.baseballprospectus.com/article.php?articleid=26195

Earned Run Average. Commonly abbreviated as ERA, it is the benchmark by which pitchers have been judged for a century. How many runs did the pitcher give up, on average, every nine innings that he pitched? If he gave up a bunch of runs, he was probably terrible; if he gave up very few runs, we assume he's pretty good.

But ERA has a problem: it essentially blames (or credits) the pitcher for everything, simply because he threw the pitch that started the play. Sometimes, that is fair. If a pitcher throws a wild pitch, he cant blame the right fielder for that. And if a pitcher grooves one down the middle of the plate, chances are that's on him too. Not too many catchers request those.

However, most plays in baseball don't involve wild pitches or gopher balls. Moreover, things often happen that are not the pitcher's fault at all. Sometimes the pitcher throws strikes the umpire incorrectly calls balls. Other times they induce grounders their infielders aren't adept enough to grab. And still other times, a routine fly ball leaves the park on a hot night at a batter-friendly stadium.

ERA doesn't account for any of that. It just tells us, in summary fashion, how many runs were -charged- to the pitcher of record. And so, a starting pitcher who departs with a runner on first gets charged with that run even if the reliever walks the next three batters. The same starter would get charged if the reliever makes a good pitch, but the shortstop can't turn a double play. And none of these runs count at all if they are "unearned?" an exclusion by which the home team?s scorer decides whether a fielder demonstrated "ordinary effort."

The list of problems goes on. Pitchers who load the bases but escape are treated the same as pitchers who strike out the side. Pitchers with great catchers get borderline calls. Guys who can't catch a break for months show immense "improvement." Guys who are average one year wash out the next. ERA, in short, can be a bit of a mess, particularly when we have only a few months of data to consider.

The problem is this: We know which runs came across the plate, but we can't tell, just from ERA, which runs were actually the pitcher's fault. What we need is a reliable way to determine which runs the pitcher deserves to be charged with. That is the challenge we took on in creating Deserved Run Average (DRA).

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http://www.baseballprospectus.com/article.php?articleid=26196

Introduction

One of the hardest parts of any statistical investigation is defining what question it is you are trying to answer.

This is particularly important when it comes to pitcher performance metrics. What is it, exactly, that you want to know? For example:

(1) Do you care primarily about a pitcher’s past performance?

(2) Are you more worried about how many runs the pitcher will allow going forward?

(3) Or do you want to know how truly talented the pitcher is, divorced from his results this year or next?

The reader’s likely response is: “I’d like one metric that excels at all three!” Sadly, when it comes to composite pitcher metrics, this might not be possible.

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