Levine: Bayes and the hit-by-pitch

From SABR member Zachary Levine at Baseball Prospectus on June 13, 2013:

When home plate umpire Clint Fagan made the decision not to eject Zack Greinke for hitting Miguel Montero with a pitch, and a subsequent decision to eject Ian Kennedy for hitting Greinke with a pitch, he was answering a couple of probability questions that umpires and eventually Major League Baseball will have to face.

It’s not a question of whether the hit by pitch was intentional or not. You’re never able to answer that question. The probability that the act was intentional from the point of view of the umpire/disciplinarian is never 0, even on the most innocuous-looking play, and it’s pretty much never unless Cole Hamels is just begging for a suspension.

After a beaning occurs, an umpire and then the MLB office are forced then to determine how likely it was that tat beaning was intentional. And there is where they have run into trouble historically. It is my view that the umpires tend to be too beholden to their own warnings and may even be trying to legislate to some unwritten rules.

The second belief we’ll get to later, but as to the first, remember, it is perfectly within an umpire’s rights to eject a player with no warning. In fact, the previous pitcher tossed for a hit batsman, Jason Hammel, was ejected with no warning in the episode I documented semi-seriously here. Inversely, just because there has been a warning doesn’t mean there has to be an ejection. In fact, the inning after the brawl on Tuesday night, Mark Ellis was hit by a pitch with no consequence.

Read the full article here: http://www.baseballprospectus.com/article.php?articleid=20926

Originally published: June 13, 2013. Last Updated: June 13, 2013.