Double Plus: Strike Zone Adjustment a Coming Catastrophe?

If you follow the D-backs and saw the news earlier this week that MLB is considering raising the bottom of the strike zone, you probably had the same initial thought that I did: that could hurt the D-backs more than any other team. If you’re a FanGraphs reader, you worked through the excellent August Fagerstrom’s excellent post identifying the pitchers that might be most affected in that scenario, and you left a little horrified. If not, skip right ahead and hit that second link there. This is the internet. We’ll still be here when you get back (and if not, you might have bigger things to worry about).

To put a crass spin on it, the bottom of the rulebook strike zone was not regularly called in the beginning of the PITCHf/x era (installed in 2007), and in comparing that “real” zone to the one we’ve seen more recently (with offense dropping off dramatically), the zone has grown by three inches or so at the bottom. To be clear, the more recently-called zone is a better match for the rulebook zone than the 2009 version — the possible effect of QuesTec and holding umpires accountable for calling the rulebook zone. We still want umpires calling a rulebook zone, but maybe, the report intimates, we want the rulebook zone to be what the zone actually was in 2009. Fair enough.

Offense is definitely down, and as Fagerstrom explains, the growth of the zone (it didn’t really move down, just expanded down) is a really big part of that. Shifting hasn’t hat anywhere near as big an effect on offense, for example, despite the very real success of shifting and its increasing prevalence. I still strongly suspect that most of the downturn in offense has been teams’ increasing value on defense; even five years ago, it was not uncommon to see a player with a slight offensive edge hold down a starting gig, despite the presence of an alternative who was dramatically better on defense. Still, strike zone is huge, here: teams might score 4.27 runs per game instead of 4.07 runs per game, as found by the great Jon Roegele (and repeated in the Fagerstrom article).

The premise of Fagerstrom’s piece, though, was that a change to the zone would affect some pitchers more than others, since some live off the bottom of the zone more than others. The premise of this piece: THE DIAMONDBACKS HAVE SO MANY OF THOSE GUYS.

It is very clear that the D-backs have instituted an institution-wide plan prioritizing ground balls, and that when they have done so successfully, it has been primarily through pitch location, rather than movement. In noting last month that the D-backs had quietly been accumulating a giant wave of ground ball minor leaguers, I ran down the list of events in the last year that all pointed toward ground balls. It’s unusual to see an organization lean into this specific a philosophy to this extent, but here we are; the D-backs are marching to the beat of their own drum. It just happens to be close to the ground.

Just think about this, friends. Archie Bradley was bewilderingly consistent in targeting one side of one low part of the strike zone when he arrived in the majors this year. Zack Godley rocketed to the majors, and when he got there, he showed what seemed to be an unsustainably high percentage of pitches outside the strike zone — primarily below the zone. This may not scream at you, but from ESPN Stats & Info, take a look at pitch frequency percentages for the D-backs staff last year, compared to the Giants:

Of the six spots at the bottom of the zone and just below it, the D-backs had a higher percentage of pitches in five — and the Giants only eked out their advantage for the sixth. As Jeff found last year, the early returns of pitching at the bottom of the zone were pretty poor for the D-backs. Hitters seemed wise to the plan, with fewer swings at low pitches and more pitches thrown by the D-backs as a consequence. Still, there’s nothing “good” or “bad” about this approach; my point is: it was the approach.

There’s no way to make a change to the rulebook version of the strikezone gradually; you change the rule, and you enforce it. Godley is the poster child of this new ground ball movement (even if Brad Ziegler is probably its prophet, and Brandon Webb its patron saint). Can you imagine what would happen to Godley’s results if he couldn’t get any swings below the strike zone, throwing it there just as relentlessly? Godley had swing rates of 58%, 48% and 45% in the three spots (see heat maps above) just under the current zone; that and the contact on pitches at the bottom of the zone were his bread and butter. Moving the zone up three inches could rob Godley of both things. Sure, hitters might still swing below the zone, but maybe only in that area that used to be in the zone — and when hitters swung at the bottom third of the zone, their miss rate (25%, 25%, 6.3%) was nowhere near what it was below the zone (64%, 36%, 44%).

This hasn’t happened yet, but if it does, it may not happen with too much warning. Here’s hoping we’re on the other side of the Contention Window.