Do Umpires Call an Unfair Strike Zone on Cubs Slugger Seiya Suzuki?

[Matthew Trueblood]

Chicago's most dangerous hitter is also one of their most disciplined. Are umpires behind the plate denying him the full value of that skill?

To many Cubs fans' eyes, it's not a question of if umpires are unfair to Seiya Suzuki, but one of why. Watching him pile up 38 called strikeouts (12th-most in MLB, trailing mostly players with 100 or so more plate appearances) and seeing a lot of 1-0 counts go to 1-1 when it looked like they could have gone to 2-0, those watchers have come to the reasonable conclusion that Suzuki is getting a raw deal. He's become a poster child, in some quarters, for the need to implement a technology-assisted strike zone, on the theory that he's a better hitter than the skills or dispositions of MLB umps have allowed him to demonstrate.

That conclusion is reasonable, based on watching games and on how our fallible human brains work, but is it supported by objective data? When you break down Suzuki's taken pitches, do the numbers show the same magnitude and direction of impact that Cubs fans perceive? It's a little bit more complicated.

Firstly, we have to acknowledge a crucial fact that is often underdiscussed in this type of debate. Suzuki swings very infrequently, overall. He's excellent at not expanding his strike zone, with a chase rate in the 94th percentile among hitters who have seen at least 1,200 pitches this season, but he's in the 10th percentile for swing rate on pitches within the zone, too. The difference between his in- and out-of-zone swing rates is actually a hair below average. By being so selective, he exposes himself to more potential called strikes on the edges of the zone.

Still, overall, there has been a slight bias against Suzuki. Its effect has been vanishingly small. According to count-sensitive framing runs above average (FCRAA), Suzuki has lost just 0.11 runs to bad calls this season, though that's a net total. Few hitters have gotten as many unfriendly calls, like this one:

Suzuki has been the victim of 28 called strikes rated as clear balls, with no higher than a 25% chance of being called a strike in a neutral setting. Only Corbin Carroll and Randy Arozarena have suffered more such calls, with Isaac Paredes tied with Suzuki at 28. On the other hand, none of those three have gotten as many called balls on pitches rated as clear strikes, with at least a 75% probability of being called, as Suzuki has. In fact, only Aaron Judge and Jonathan India have gotten more of those friendly calls than Suzuki, on pitches like this:

Here's where things really get interesting. Obviously, Suzuki forces umpires to make more close calls than almost any other hitter in the league. He's gaining a lot of value on some borderline pitches, and losing a lot of value on others, and much of it washes out. Fans see all of these pitches, when they watch games, but they tend to give Suzuki credit for close takes when the call goes his way, yet blame the umpires when the call goes against him. That's natural; it's a blend of various patterns in the way our brains work. Still, it's distortionary. Some substantial share of the perceived unfairness to Suzuki by umpires is really just the way fans experience randomness--as a cruel and biased force, rather than a chaotic but essentially fair one.

That would be true, at least, except that there is a pattern to the errors umpires make on Suzuki--or, more plausibly, an error in the way we're capturing their calls. Here's how Suzuki's Strike Looking Above Average rate looks, based on the location of the pitch:

Maddening though it is for many fans, the top and bottom of the strike zone are essentially subjective. The horizontal zone is bounded by the edges of home plate, and when a pitch is off the plate, it has to be counted as a ball. The vertical zone, though, only has theoretically solid boundaries. How a hitter stands in the box partially determines where those boundaries are set, and even then, we're asking the umpire to judge the location of the ball with respect to those boundaries, without very good visual markers to set it.

Thanks to choices made by production trucks throughout MLB, the white box dominates the way we watch the game. A more accurate version of it also delineates balls from strikes in models like the one rating Suzuki's zone as basically neutral. It helps that such models treat pitches near the edges probabilistically--i.e., that a pitch called a strike in a location where it would be one just half the time only counts as an extra half a strike against Suzuki for the purposes of evaluating how he's officiated--but those models still assume that all pitches at a given vertical location to a hitter of a given height have the same chance of being called a strike. Pretty clearly, that's not true. Here's a very typical called strike against Suzuki, that (according to the modeled zone, with its firm but subjective bounds) ought not to have been:

Certainly, based on how he's reacted to them throughout his career, Suzuki doesn't think that should be a strike. The model doesn't think so, either. When you see where it's caught, though, does it really look extreme or egregious--except in that it's above the magic white box? Meanwhile, here's a pitch that wasn't called a strike, but clearly should have been, based on the model.

This pitch wasn't well-framed, which can always be another confounding factor, but it does clearly nip the bottom edge of the box. At the same time, it doesn't feel like an egregious miss, does it?

If you cut the zone in half vertically, the numbers for Suzuki leap flying off the page. In the upper half of the zone (roughly speaking, anything above the belt), Suzuki has had 34.8 extra strikes called against him this season. That's the highest number among the 208 batters who have seen at least 500 pitches in those locations this season. His -5.3 FCRAA in the upper half of the zone is also the league's outlier; umps have taken 5.3 runs from him at the top edge.

In the bottom half of the zone, though, the men in blue have given Suzuki 5.2 runs, which is the highest figure of the 294 batters with at least 500 pitches seen below the belt. They've given him, on balance, 25.2 extra balls in those locations. It all nearly comes out in the wash.

To that observation, add this one: Suzuki swings considerably more at pitches up in the zone. His overall swing rate is higher, 45.1% to 36.6%. So is his swing rate on pitches with between a 20% and an 80% chance to be called a strike, based on framing models, 53.6% to 34.3%. The logical conclusion from all these observations is not that Suzuki is being robbed, or that he's being too passive. It's just that we need to stop treating the strike zone you see on TV for him as accurate.

For whatever reason, based on how he stands in the box, how he swings, or some other inscrutable factors, umpires clearly perceive his zone to have higher bottom and top edges than the computers have dialed in. Suzuki agrees. Look at his swing rates by location, or just a heat map of his swing rate, and you see a hitter who thinks of some pitches just above the zone as within his eager reach, and some within it at the bottom edge as unworthy of him.

If the umpires and Suzuki agree, when it comes to the vertical bounds of the zone, arbitrary computerized zones shouldn't intrude on the arrangement. Pitchers can't really exploit this, because if they aim for that bottom edge of the zone that Suzuki disdains, umpires won't call it. If they aim for the top of the zone, they might steal a strike now and then, but Suzuki is also waiting to pounce on a mistake in that region. 

The horizontal zone has to be called objectively; we have a good way to define it. But with a few exceptions, Suzuki's horizontal zone has been called fairly, throughout his career. It's the high and low pitches that have yielded consternation, and the appearance of unfairness. That consternation is unnecessary, and the appearance of unfairness is deceiving. The Suzuki strike zone is a good reminder that technology isn't ready to call balls and strikes especially well, in one dimension, and that doing so isn't a matter of simply drawing an imaginary line at two fixed vertical positions for a player based on their height. The game is more beautiful and more complicated than that.

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