Robo strikezone: Not as simple as you think -- Baseball Prospectus

Mystic Merlin

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Sep 21, 2007
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The reason for a strike zone is so batters don't let hittable pitches go by. If a pitch is not in a hittable location, then it shouldn't be a strike, regardless of what the rule book defines it as. Umpires, pitchers, and hitters have all come to an agreement one which should count and which shouldn't. Umps don't have personal zones nearly as much as they used to. It's all pretty uniform now, just with rounded corners.

We keep saying "they're professionals, they'll adjust." But sometimes they can't. Strikeouts are higher than ever and nobody was able to routinely beat the shift when it was allowed. Putting balls in play is really hard. We shouldn't be doing anything that makes it harder.
I’m not sure any of this is true re: the zone. My kind is reeling at your suggestion that if a pitch is a strike by rule the ump - apparently in some collaboration or quid pro quo with the pitchers and hitters? - it shouldn’t be called if it isn’t ‘hittable.’ I’d say, advocate to change the rules of the zone if it is too big. But that aside, what determines whether a pitch is ‘hittable’? The zone already accounts for a player’s height, so are you talking about width?
 

joe dokes

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Jul 18, 2005
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I was surprised that pitch was a strike.
Does the zone change vertically to assess "knees to armpits" (or whatever the official zone is) when Fred Patek follows Frank Howard in the lineup?
 

SumnerH

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I was surprised that pitch was a strike.
Does the zone change vertically to assess "knees to armpits" (or whatever the official zone is) when Fred Patek follows Frank Howard in the lineup?
Writeup over here, but they definitely have different zones. There are multiple options for how to set those zones that they're playing with: the Hawk-Eye system includes skeletal tracking to follow a player's height and crouch in real time. They can use that data to set a zone based on the batter's stance, or they can just set the zone to standard percentages based on the batter's height. AAA is doing the latter this year, Florida State League the former. Presumably they'll evaluate which is better after the season.

Also of note: the zone being used is a two-dimensional rectangle at the midpoint of the plate The width used varies between the leagues (it was narrowed for AAA last year to the actual home plate width, after making it a bit wider last year resulted in a ton of Ks).

The strike zones for Triple-A and the Florida State League will be different. In Triple-A, the strike zone will be 17-inches wide (the width of the plate) with a two-dimensional rectangle at the midpoint of the plate. The top and bottom of the strike zone will be set at 53.5% and 27% of the batter’s height. While the width and bottom of the zone are the same as last year, the top of the strike zone has increased by 2.5%.
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In the Florida State League, the zone will be quite different. Most importantly, the width of the zone in the FSL will be 20 inches (three more than in Triple-A). Like Triple-A, it will be measured as a rectangle set at the middle of the plate.
The top and bottom of the zone will use the Hawk-Eye visual tracking system. The bottom of the zone will be set to the height of a hitter’s back knee, while the top of the zone will be set based on the midpoint of a batter’s hips, with the goal of making the top of the zone equal to one baseball above a batter’s belt. If a hitter’s stance changes, the strike zone will change as well, but it will be based on a rolling median of the hitter’s stance on previous pitches that have been put in play. So a hitter who tries to manipulate the zone by taking pitches but not swinging from an exaggerated crouch will not be rewarded.
 
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jon abbey

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To compound it, he called Gleyber out on the same pitch in his second AB also. I would have lost it.
 

Sad Sam Jones

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Yankees beat the Guardians 3-2, with the save going to the home plate umpire who called ball 4 as strike 3 with a runner on 2nd and 1 out. The pitch was way inside and the catcher did nothing to frame it.
 

jon abbey

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Although the next batter grounded the first pitch hard right at the 2B, of course you can’t assume he does that if Florial had walked, but if he had, easy DP.