Murphy: Leverage matters: When to invest in the bullpen

From Matthew Murphy at The Hardball Times on August 20, 2014:

Who was the best pitcher in the American League in 2013?

By WAR, it was Max Scherzer, although teammate Anibal Sanchez had a better ERA, and Yu Darvish had more strikeouts. King Felix and Chris Sale also had excellent seasons and could be considered. One name you might not expect to hear is Greg Holland, although by one measure, he helped his team win games more than any other pitcher in the Junior Circuit.

Baseball statistics exist on a spectrum from predictive to descriptive. Pitching metrics like SIERA and xFIP try to predict future outcomes based on exhibited skills. Moving down the spectrum, FIP and ERA describe what happened, in terms of the pitcher’s K/BB/HR or total runs allowed. Near the end of the spectrum is a statistic that best describes how a player influenced his team’s chances of winning each time he played: Win Probability Added (WPA).

It is by this metric that Greg Holland led the AL in 2013.

Let’s be clear: I’m not saying that Holland is better than or even close to being as valuable as Scherzer, Darvish and Sale. This just illustrates that his contribution to his team’s record was greater than any other pitcher’s. In fact, if you look at the pitching leader boards and sort by WPA, relievers routinely place very highly on the list, including seven of the top 10 in 2013.

This is one of many arguments used when people claim that WAR systematically undervalues relief pitchers. To some degree, this is a valid point. Having an elite reliever to pitch in high-leverage situations can be have just as much of an impact on a team’s performance as having a dominant starter. Plus, since leverage is largely determined by the manager, it actually has a higher year-to-year correlation than performance metrics like FIP and xFIP, making it both predictable and repeatable. However, if a team has a second similarly skilled reliever who could have taken care of those high-leverage innings with similar proficiency, then the first pitcher doesn’t seem quite as valuable.

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Originally published: August 20, 2014. Last Updated: August 20, 2014.