While Major League Baseball has expanded its replay system in an effort to reduce incorrect calls made by umpires, the strike zone remains the most frustrating aspect of a baseball game and new research shows why.
According to rule 2.00 of the Major League Baseball rule book, a strike zone is defined as “that area over home plate the upper limit of which is a horizontal line at the midpoint between the top of the shoulders and the top of the uniform pants, and the lower level is a line at the hollow beneath the kneecap” and is determined by “the batter’s stance as the batter is prepared to swing at a pitched ball.”
Here is the diagram that accompanies the definition:
However, what umpires actually judge to be the strike zone is different even though they are getting better.
In a research paper examining the performance of Major League Baseball umpires, Brian M. Mills of the University of Florida shows what pitches are actually called strikes.
The diagrams below, reproduced with the permission of the author, show the strike zone from the umpires point of view. Balls thrown inside the green line were called a strike more than 50% of the time and what we see is something that looks much more like a square strike zone (or even a circle) and less like the rectangle portrayed above.
As shown by Mills, the strike zone has evolved since 2007, the year when Major League Baseball began using Pitch f/x technology to monitor the speed, movement, and location of pitches. The actual strike zone has become a little more narrow and umpires are more likely to call strikes lower in the zone.
But there are still problems.
The biggest issue is that umpires have a different strike zone for left-handed and right-handed batters. The data shows that right-handed batters are more likely to have an inside pitch called a strike and left-handed batters are more likely to have an outside pitch called a strike.
Players and managers always say that the most important criteria for an umpire calling balls and strikes is consistency. However, this data shows that even though umpires now have a strike zone that is starting to look more like the rule book there are still inconsistencies in how it is called.
Even with the expansion of the replay system, it is still hard to imagine a time when something other than umpires are calling balls and strikes. But as we get better at seeing how often the umpires are wrong, something will eventually need to be changed.
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