Prospectus Feature: Francisco Liriano, Chase Rates, and Global Trade

In this article, I explained that batters are swinging at pitches outside the strike zone less frequently this year, reversing a fairly steady recent trend, and that this has particularly hurt pitchers whose strategy has been to pitch outside the zone, inducing weak contact. It’s also affected teams (notably the Pittsburgh Pirates) whose pitching staffs focus on getting batters to swing outside the strike zone.

So if pitchers who depend on inducing swings outside the zone are the victims of this shift, what kind of hitters are the beneficiaries?

In the earlier article, I listed the pitchers with the lowest Zone Rate (percentage of pitches in the strike zone) in 2015 and how they’ve fared this year. (Short answer: Worse.) Zone Rate might seem like a proxy for control, but it isn’t. Well, it might be for a pitcher called up for a couple weeks who can’t throw strikes, but pitchers who accumulate a lot of innings with a low Zone Rate are doing it strategically. They’re trying to get batters to chase pitches outside the strike zone. The leaders last season included Liriano, Dallas Keuchel, Jon Lester, and Felix Hernandez, good pitchers all. (At least they were last year.)

In looking at hitters, though, Zone Rate is the wrong metric. Here’s a list of the 15 batters with the lowest Zone Rate in 2015 (minimum 400 plate appearances). For each, I’ve listed their 2015 Zone Rate (Zone), swing rate on pitches outside the strike zone (O-Swing), and Total Average (TAv), BP’s league- and park-adjusted measure of total offensive value scaled to an average of .260. I’ve also listed 2016 totals through the All-Star Break (minimum 200 plate appearances) and the difference between the years.

See what I mean? The hitters with the lowest Zone Rate are, by and large, excellent hitters. Pitchers avoid the strike zone because they don’t want to give them anything to hit. They had a .290 average TAv in 2015, and they’re doing better this year. So Zone Rate’s not the way to identify batters who’ve benefited from the trend to lay off pitches outside the zone.

At first blush, it’d seem that the hitters most prone to chase pitches outside the zone would benefit from this shift. Here’s a list of the 15 hitters who, in 2015, were the most likely to swing at pitches outside the strike zone. They’re in decreasing order of 2015 O-Swing rate.

Hmm. That’s not really persuasive, is it? On average, the batters who chased the most last year have a TAv 8 points higher in 2016 than 2015. That’s good, but it’s not overwhelming, not like the 0.71 increase in ERA and 0.62 in DRA from 2015 to 2016 for the 15 pitchers with the lowest Zone Rate. There are some major success stories there (Jean Segura, Jose Altuve, C.J. Cron, Salvador Perez), but of the 15 batters, six are worse than they were last year.

But maybe that’s not the right way to look at it, either. Erick Aybar, for example, has been worse so far in 2016 than he was in 2015, and he’s chasing more this year, not less. So let’s look at the 15 players with the largest reduction in O-Swing rate, in that chasing fewer pitches outside the zone should yield greater success:

These are the 15 batters who’ve exhibited new-found discipline on pitches outside the strike zone. Francisco Liriano’s run into problems because his O-Swing rate has fallen from 33.0 percent last year to 28.0 percent this year and his TAv allowed has shot up .234 to .304. The top 11 batters on the above list are the reverse Lirianos: They’ve reduced their O-Swing rate by more than the decline Liriano’s experienced. And yet, for those 11, their efforts have resulted in a TAv that’s, on average, .016 higher than in 2016. That’s good—it equals the difference between 2015 Nolan Arenado and 2016 Nolan Arenado—but again, it’s not an extreme improvement, and it’s nowhere near Liriano’s increase. There are 163 batters who had at least 400 plate appearances last year and 200 this year. Of them, 60—that’s 37 percent–have a TAv in 2016 that’s at least .016 higher than in 2015. A .016 increase isn’t an outlier. Cutting down on high O-Swing Rate is correlated with success, unsurprisingly, but not outsized success.

So maybe there’s something else involving being pitched in the zone and chasing outside of it. Here are the 15 players with the largest TAv increase from 2015 to 2016.

Nope, nothing here either. The 15 players who’ve improved the most so far this year are seeing about the same proportion of pitches in the strike zone, and they’re chasing only slightly less frequently (a third are chasing more).

So what’s the relationship? We’ve established that with batters swinging less often at pitches outside the zone, pitchers who are dependent on those swings are faring disproportionately worse in 2016. But how about batters? There don’t seem to be reverse Lirianos, a subset of batters who are disproportionately benefiting by laying off pitches outside the zone.

The costs of batters chasing less frequently are concentrated. Some pitchers—Liriano, Kyle Gibson, Keuchel, Wade Miley, James Shields, Jorge De La Rosa stand out—are doing much worse in 2016 than in 2015, and they ranked 1-6 in lowest Zone Rate in 2015. They’ve allowed a TAv that’s, on average .040 higher in 2016 than 2015. That’s a Kyle Seager-level difference. For batters, though, the benefit is more diffuse. Some, like Segura and Altuve, are chasing less and hitting more. But it’s not uniform—nobody’s reduced his chase rate more than Todd Frazier, and he’s been a worse hitter this year than last year—and the improvement, on average, is far eclipsed by the decline in performance by the most chase-dependent pitchers. That combination—concentrated costs and diffuse benefits—is a characteristic economists ascribe to global trade pacts. In that way, it would seem, Francisco Liriano and NAFTA opponents would seem to have common ground. For pitchers, a low Zone Rate would appear to be a warning sign in 2016 baseball. For hitters, though, a declining chase rate, while certainly a good idea, doesn’t guarantee success.