September 29, 2017

Rubbing Mud

What Happened to the High Strike?

by Matthew Trueblood

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Last week, I wrote about the rising frequency of hit batsmen and catcher interference, within the context of the ever-growing league-wide emphasis on velocity and power. The gist of the piece was that the fight for control of the strike zone seems to be taking place in a smaller space all the time, and that the stakes of that battle are higher than ever.

One commenter had an idea for solving this problem (insofar as it is a problem; I don’t feel that it is):

Honestly, I’m not sure what that second part means. I haven’t witnessed any batters standing beyond the back line of the batter’s box, and if that ever becomes a problem, I don’t think MLB will hesitate to take some action. I also wonder if this commenter has considered the implications of either of these proposed changes. They would both reduce offense, and if you strip away the distortion of the home run spike, offense is already endangered. The game this person is advocating is probably an even less balanced one than what we have right now.

The first part is interesting, though, because this is a very, very frequent complaint, especially from fans who have been watching the game for decades. We know the strike zone expanded from about 2011 through 2015, and we know it mostly expanded downward. Since the last home run spike, in the mid-90s, people around the game have been calling for a more consistent, larger top portion of the strike zone, believing the game moves faster and is more balanced when the high strike is called more often.

I decided to look further into the matter. Baseball Savant has a Statcast tool that searches based on pitch location. One can use the standard, nine-box strike zone (and four-box out-of-zone grid) provided by MLB’s Gameday module, or more detailed zone segments laid out in the tool. I chose the latter, and queried to find the percentage of all pitches along the topmost ribbon of the zone (theoretically, in fact, it’s a set of zones that straddle the edges of the zone, such that we shouldn’t expect more than about half of those pitches to be called strikes, when taken) at which the batter did not swing, and which were called strikes.

Called Strikes as Percentage of All Taken Pitches, Top Edge of Strike Zone, 2009-2017

Season	Called Strike Percentage
2009	32.9
2010	27.8
2011	33.0
2012	29.3
2013	30.6
2014	30.0
2015	24.9
2016	26.2
2017	28.5

One reading of this would certainly be that the called high strike really did disappear a few years ago, and is only slowly returning. I’m not ready to say that. The data seems awfully noisy, especially prior to 2015. In fact, based on this information, the only thing I would tend to believe is that the strike zone already is expanding at its top. The difference is small, but I think it’s meaningful.

When a pitcher works up in the zone, a called strike is not the objective. Most of the time, they want to work up and out of the zone, but draw a batter’s swing, thereby getting a whiff or a pop-up. They might occasionally try to throw a knee-buckling curve that ends up in the top portion of the zone, but mostly working up is about inducing swings, so any change toward more high strikes being called (even a small one) will force the hitter to protect that area more, and is likely to increase the hurler’s chances of getting that swing.

If the zone is generally more open at the top, that also allows pitchers to work up there more consistently. That, in turn, could force more hitters to alter their power-over-contact swing mechanics and approach, and to focus more on a quick swing that can deliver quality contact consistently. That’s been a big driver in the move toward more high fastballs and more curves, over the last year and change. Pitchers believe they can reshape hitters’ approaches and make them less dangerous by forcing them to modulate their swing and de-emphasize lifting the ball.

The trend (unprovable but, in my opinion, fairly obvious) toward batters standing closer to the plate comes into play here. Pitchers know hitters are getting more plate coverage, and that the closer they stand to the plate the less they tend to be fooled by horizontal movement differentials. That’s nudging pitchers toward more high strikes and more eye level-changing vertical breaking balls.

If pitchers are working more often this way, they’re probably also learning to command that pitch better, and their catcher is probably getting both better at framing the pitch and politicking with the umpire to gain more calls in that area. Thus, it’s not simply that umps might be loosening the lid on the zone, but that pitchers might be doing that themselves, out of necessity. The global adjustments have been happening quickly for years now, but if more and more pitchers really do learn to pound the top part of the zone, it might be a long time before batters can totally adjust.

Flattening the average swing might make it quicker and better able to get the good part of the bat to the ball, but it also generates more ground balls and low line drives. In this era of aggressive defensive shifting and shading, players are less likely than ever to intentionally hit the ball in that way. If pitchers can consistently work the top of the strike zone, batters are in big trouble—juiced ball or not.

Matthew Trueblood is an author of Baseball Prospectus. Follow @MATrueblood
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