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May 01, 2007

Brandon McCarthy, Part 2: How Much Of The “Suck� Is Bad Luck?

The pitch data presented in the previous entry doesn’t tell much of the story behind McCarthy’s dreadfulness this season. This table does:

Year
HR%
BB%
SO%
BABIP
ERA
LERA
2005-2006
 4.8% 7% 19% 0.259 4.41 4.72
2007
 2.9% 10% 12% 0.382 9.90 6.69

Despite pretty similar ball-strike distributions, McCarthy has walked more and struck out far fewer batters than during 2005-2006. The real killer is the gigantic increase in average on balls in play. He was a bit lucky in Chicago (where typical BABIP is about .290) and has been hugely unlucky in Texas, where a BABIP of about .305-.310 is the norm. If not for some improvement in home runs allowed, his ERA might be near 12.00.

So, the question is, how much of his meltdown is due to him alone, and how much is simply bad luck? It’s impossible to say for sure, but the last column of the table provides a little bit of an answer. LERA stands for Latent ERA, a stat I’ve used in the past but didn’t name until now. (If there’s anything baseball needs, it’s another obscure statistical acronym.) It’s a combination of Bill James’s Component ERA (except adding actual data for doubles and triples allowed instead of estimates) and DIPS (except adjusting to the BABIP typical for the team, not the league). Basically, I’m trying to estimate what the pitcher’s ERA might be assuming a typical distribution of baserunners and a typical BABIP for his team.

McCarthy appeared to be a bit lucky in Chicago, as evidenced by the slight increase in his LERA compared to his actual ERA. In Texas, his ERA “ought” to be 6.69 rather than 9.90. Depending on how the numbers are examined, perhaps 60-65%% of the increase in ERA is bad luck, and 35%-40% is purely his own fault.

This is ultimately an exercise in numerical tomfoolery, and goodness knows I’m not suggesting that McCarthy’s pitching is acceptable. However, if his ERA were actually 6.69 instead of 9.90, people might only be saying “he needs to get his butt in gear” instead of “he needs to be euthanized.”

Posted by Lucas at May 1, 2007 06:43 PM