The average strike zone in 2016 was similar to 2015’s in size and shape, finally giving MLB players some consistency from year to year. From day to day, though, their strike zone may have changed as different umpires called balls and strikes, each with their own tendencies and preferences. How much did umpires’ personal strike zones differ in 2016?
I took the umpires who called at least 30 games in 2016 and calculated the size of their strike zone, compared to the league average. Briefly, I divided the area around the strike zones for left- and right-handed batters into three-inch squares, asked how many pitches each umpire saw in each zone and how many he called strikes, and then compared to the percentage of strikes in that box across all baseball. The end result is expressed as “extra strikes per game”, compared to what an absolutely average umpire would have called. The full list is here.
The three umpires with the smallest strike zones (the most batter-friendly) were Jerry Meals (who called 3.7 fewer strikes per game than the average umpire would have), Joe West (-2.6), and Alfonso Marquez (-2.5). The three largest zones belong to Bill Miller (4.4 extra strikes per game more than the average umpire), Mike Estabrook (3.8), and Jim Wolf (3.6).
Umpires are generally fairly consistent year over year, with the same umpires tending to have large or small strike zones. Joe West has called a smaller-than-average zone for the past six years; Miller has had a larger-than-average strike zone every year since 2008, when PITCHf/x was fully available.
We can look at umpires’ calls in more detail by plotting differential strike probability. In the following charts, each square is colored red to indicate if an umpire is more likely to call pitches there a strike, or blue if they are less likely. The intensity of the color reflects the difference in likelihood.
Here are what Jerry Meals’s and Joe West’s small strike zones look like:
Both of them are less likely to call strikes for left- and right- handed batters. West actually is slightly more likely to call strikes inside to righties or outside to lefties, and Meals shows a similar, though weaker, trend. Both of them, but especially Meals, have stronger tendencies for lefties, since the colors on the RHB plots are relatively muted.
Here are the large strike zones of Bill Miller and Mike Estabrook:
These are just big zones, to all batters and on all sides of the zones.
Even for umpires who call a nearly neutral zone overall, there may be preferences for certain regions. Here is Chris Conroy, who has dramatic differences in the way he calls strikes to left- and right-handed batters, but ends up almost exactly average (-0.2 extra strikes per game overall):
To left-handed batters, Conroy calls quite a large strike zone, but righties have a small one.
Most umpires have slight preferences, but few are as dramatic as the ones I’ve mentioned here; the majority are essentially neutral. Here is the distribution of extra strikes by umpire:
Of the 67 umpires who called 30 or more games in 2016, more than half (37) were within one strike per game of being average in either direction, and only 13 were more than two strikes per game away from average.
Check out the complete list to see how umpires’ strike zones have changed over the past several years by clicking here.