April 10, 2015

The Strikeout Indicator Failure

A high strikeout rate often indicates an effective pitcher. Strikeouts reduce the number of balls in play, which should lead to fewer hits, since on average batted balls get turned into hits somewhere between 29 and 30 percent of the time. We usually measure this with batting average on balls in play (BABIP, (Hits-HR)/(AB-(HR+K)). Pitchers over .300 for a season might have been a bit unlucky, as maybe their fielders didn’t help them. Pitchers under .290 might have been a bit lucky, maybe playing in front of a great defense. Of course, the same skills that cause pitchers to miss bats may also cause hitters to hit the ball poorly, so the best pitchers have somewhat lower BABIPs that average pitchers.

When I see a high strikeout rate in a game, I will be surprised to see a high hit count along with it. This happened to CC Sabathia on Thursday. He struck out eight in 5 2/3 innings, but also gave up eight hits. This Friday afternoon, it was a bit worse for Zach McAllister. He struck out five Tigers in four innings, which should be pretty good. But he allowed 13 hits, one of them a home run. He faced 25 batters, and they recorded 23 at bats. So his BABIP for the game was 12/17 or .706.

That made me wonder what are the extremes here. I looked for games started by a pitcher in which he faced at least 20 batters and had a strikeout rate of at least 7.0 per nine IP. The highest in game BABIP that met those criteria belonged to A.J. Burnett on 6/26/2010, pitching for the Yankees against the Dodgers. He struck out five in three innings, but walked six, and batters went 6 for 7 on balls in play, giving him a .857 BABIP. That the worst of five games where high K pitchers allowed a BABIP of .800 or better since the mound was lowered in 1969. All in all, he’s the 69th pitcher in that time period with a game BABIP of .706 or higher with a high strikeout rate.

The Tigers lead the Indians 8-3 in the bottom of the eighth inning.

2 thoughts on “The Strikeout Indicator Failure

  1. Steve H

    A high strikeout rate per inning is not as impressive if calculated as strikeout rate per plate appearance. Obviously per inning is easiest to find, but nowadays strikeouts per plate appearance should be available and would be a more accurate index.

    ReplyReply

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