The Pitchers Hurt Most by a Higher Strike Zone

Major League Baseball has been floating a bunch of different ideas lately to help improve the game: automatic intentional walks, starting a runner on second in extra innings, and one that would likely have the most impact, raising the lower bounds of the strike zone.

If you feel like you’ve heard that last one before, it’s because you almost definitely have. Jon Roegele has been chronicling the expansion of the strike zone for years. It’s not just him, though. Just last year, there were reports that MLB planned to raise the strike zone. In response, August Fagerstrom discussed who might be affected the most. August isn’t around these parts anymore, so consider this post your update on the pitchers who might be negatively affected by a slightly higher strike zone.

First, consider the visuals below. They’re from a 2014 piece by Roegele and were reproduced by Fagerstrom last year. They documents how the strike zone has expanded downward over the last decade.

It’s pretty obvious from these graphs that pitches in the lower part of the zone were being called strikes more often in 2014 than five years earlier. But these images are from a couple seasons ago. Is it possible, given the talk last season about raising the strike zone, that umpires took it upon themselves to do it? To compensate for the lower-zone creep happening of late?

It’s a reasonable theory, just not one that can be substantiated by evidence. Roegele recently updated his work to include last season. The results? The strike zone is still rather large, especially at the bottom of the zone.

There was still a pretty high frequency of low strikes last season. Forcing pitchers to work higher in the zone, even by a few inches, would increase the number of swings batters are compelled to take and increase, at the same time, the number of balls in play. That’s the theory anyway.

If pitchers, facing a new zone, were nevertheless to approach hitters exactly as they did in 2016, the result would probably just be more called balls. Last season, in the low part of the zone between 1.50 and 1.75 feet above the ground, batters swung at 48% of pitches. In the area directly above it, though — between 1.75 and 2.00 feet — batters swung at 53% of pitches, per Baseball Savant. Of course, if pitchers are trying to hit the new lowest part of the zone, batters are more likely to swing in the area between 2.00 and 2.25 feet (57%).

It’s not just swings. As the table below illustrates, hitters make more contact at pitches up in the zone.

Both swing rate and contact rate increase the higher a pitch gets in the strike zone. That’s pretty intuitive, of course: the closer a pitch is to the middle of the strike zone, the easier it is to hit. Assuming pitchers don’t want to throw more balls (and they don’t), they’ll be forced to throw more pitches slightly higher in the zone, which would presumably lead to more swing and more balls in play. It’s possible that hitters would adjust begin to offer at fewer pitches in the lower part of the zone. Possible but unlikely. Hitters swing at these pitches not just because they’re strikes, but because they’re good pitches to hit.

Let’s return briefly to the table above. In addition to swing rate and contact rate, another metric that increases with pitch height is slugging percentage. That starts at .354 in the 1.50- to 1.75-inch rage, up to .428 in the range above that, up to .499 in the range above that. If you believe that the strike zone should be comprised of the most hittable pitches, it isn’t clear the lower part of the current strike zone fits that description.

Last year, August hypothesized that the pitchers who would be affected the most are those who work most often in that lower part of the zone. Among the starters pitching low in the zone were Carlos Carrasco, Kyle Hendricks, Mike Leake, Jon Lester, and Alex Wood. Repeating that exercise with 2016 number produces the following results for starting pitchers.

Many of the same names carry over from last year. Now here’s the same table, except for relief pitchers.

These pitchers are still likely to utilize the same area to get swings, and it isn’t like moving his pitches a couple inches up is going to make Andrew Miller a bad pitcher, but as strikeouts have continued to go up and up over the last 10 years, getting the strike zone back to where it used to be is probably the easiest answer to curtailing that trend. (Expansion might be another answer, but it isn’t quite so simple.) Walk rates haven’t changed too much since the strike zone got bigger, so there isn’t a ton of reason to think that decreasing the strike zone will lead to a lot more walks.

Expanding on the charts above, here are the pitchers who would have lost the most called strikes last season.

At the other end of the spectrum, there are also pitchers who are not likely to be affected by a change in the lowest part of the strike zone. The group below, including both starters and relievers, rarely pitched in that area last year.

We know that the strike zone has gotten bigger, and that the area where the strike zone has grown tends to elicit (a) fewer swings, (b) more swinging strikes, and (c) a lower slugging percentage than other areas of the zone. We know that strikeouts keep increasing. The solution seems pretty obvious. It will affect the way pitchers pitch, and the way hitters hit, but for those who enjoy seeing the ball put in play, it is a sacrifice that pitchers, some more than others, will have to make for the sake of improving the game.