So this table shows the lowest BABIPs recorded in the past five years by qualified pitchers who also posted a ground ball rate of 53 percent or higher.
You’ll note that both world-beating 2015 Cy Young winners are present, along with the last dominant season we’ve seen from Felix Hernandez, and the breakout 2016 performance of young Blue Jays starter Aaron Sanchez.
It is Sanchez that I wish to discuss, but the other seasons there have been presented for a reason. Namely, they didn’t repeat themselves. They didn’t come close. Arrieta’s 2015 ground ball rate was a personal outlier to begin with, so he went back to a more balanced batted-ball mix in 2016. Felix actually kept his ground ball rate the next year, but his BABIP jumped up 30 points into normal territory, as you’d expect, and his home run rate spiked. Keuchel, whose plight has been much discussed, maintained a less-elite-but-still-elite ground ball rate in his follow-up season, 2016, but saw his performance crater as the bottom of the strike zone edged upward and a boat load of called strikes vanished.
To summarize the anecdotal evidence above: Sanchez is probably not going to roll merrily along in Cy Young contention with his current profile.
You’d probably also reach that conclusion by perusing your favorite performance based peripheral. Among pitchers who threw 120 innings last year, Sanchez ranked 69th in K-BB% (which is not nice, unless you were hoping he’d be firmly in the middle of the 118-pitcher pack). His swinging-strike rate ranked 101st (!). If you checked the comprehensive Baseball Prospectus metric DRA, he slotted in at a slightly more optimistic 45th among the same group.
With that cold water having rid you of recency bias and ERA fixation (yes, that 3.00 was round and beautiful) let’s try to figure out if Sanchez is doomed. Or, more politely, let’s see where he is likely to go from here.
Simple mental exercise: You are a hitter, and you know the starter you’re facing today is one of the league’s premier ground ball pitchers. What’s your plan? One way to go would be to avoid swinging at the low pitch — kind of like the strategy you hear for hitters facing knuckleballers.
Of course, that doesn’t really work. For one, two-seam fastballs and sinkers and the like come in much faster than knucklers. For another, they are often deployed as part of repertoires that also include four-seam fastballs or other pitches that look similar out of the hand before doing something entirely different as they approach the plate.
This is why hitting is not, in fact, a simple mental exercise. But hitters do learn, and do adjust to pitchers — perhaps especially pitchers with extreme tendencies. It’s just not clear exactly how.
Take Keuchel, for example. It was very well known that his success in 2015 was built on grounders and low called strikes. In 2016, his regression would suggest that hitters figured out how to handle those pitches, but the numbers paint a weird picture. They didn’t actually do much better at spitting on his low sinkers. Per Baseball Savant, hitters swung at 25 percent of Keuchel’s pitches that were outside the bottom half of the zone, compared to 26.4 percent in 2015. They swung at 60.1 percent of sinkers in the bottom third of the zone, compared to 61.4 percent in 2015.
The discipline didn’t really change, but the drop in called strikes forced Keuchel to throw higher pitches, and hitters opportunistically proceeded to throttle them, even his bread and butter.
And when I first looked at Sanchez’s ground ball rate by month, which declined steadily and noticeably from May through the end of the season, I couldn’t help but wonder if the league was adjusting to his success, too.
Then I ran into a reason to think that’s not exactly what was happening.
This plots ground ball rate against the proportion of a pitcher’s offerings thrown low (in the bottom third of the zone, or outside the lower half, per Baseball Savant). It shows only a mild correlation, but two dots stood out: The ones that induce elite worm-killing numbers while aiming low with just a little more than 45 percent of their pitches.
One is Sanchez, and the other is Cardinals hurler Carlos Martinez.
Several similarities emerge: They had two of the three hardest two-seamers in the majors last season, among starters, and they rate very highly in horizontal arm-side movement. Here I’m indebted to Gerald Schifman’s excellent piece from this past summer in The Hardball Times, which illustrated how different factors such as velocity and movement affect ground ball rate. I’m borrowing his chart here, just to point out that Sanchez and Martinez posted horizontal movement numbers that can be found on the business end of that hockey stick.
So we have a general idea of how he’s producing grounders without just pounding the bottom of the zone. If the object of the game were to get ground balls, throwing high is still not the choice you’d make, even with Sanchez’s velocity and movement. Luckily, that’s not the object of the game!
Instead, Sanchez stands to benefit by being less restricted in locating his two-seamers, allowing him more freedom, theoretically, to play off his other pitches and create confused swings. That’s an unproven assertion, but it seems to manifest itself in the results from last year. Take a look.
Against right-handers, his two-seamer can elicit swings that end up overextended — useless reaches for a ball that is actually tracking back into their body.
Against lefties, it functions differently, but functions all the same — drawing swings only to dart to the outside corner and ping off the end of the bat.
The results also show up in the numbers. Sanchez allowed a .388 SLG on two-seamers/sinkers in the middle third of the zone (AKA the blast zone). That clearly beat the league average .555 SLG for two-seamers/sinkers in those areas, and ranked 5th among pitchers with at least 50 of those pitches put in play (Martinez and Arrieta were among those ahead of him). What’s more: Sanchez had 129 put in play, a huge sample (second in baseball) that suggests he was quite comfortable using the pitch to challenge hitters.
Baseball comps, while fun, are usually more misleading than useful. For the sake of visualization, however, I’ll offer the theory that Sanchez could follow more in Martinez’s path (which is itself not very long) than those of other recent ground ball mavens who came crashing back to earth.
That comes with the caveat that even adhering to Martinez’s recent performance will look like regression, despite the context-neutral metrics saying they were quite similar last season.
Arrieta, another data point from the beginning of our journey today, also blazed an interesting path. He was actually able to lower his BABIP in 2016 by replacing grounders with fly balls and the accompanying popups, a profile Sanchez actually displayed for a brief stretch in July. Arrieta’s changes, though, came with control issues (which Sanchez is all too familiar with) and resulted in disappointment on the whole.
Ultimately, the point is that relying on a certain batted ball mix is a risky business. It adds an extra layer to the game of getting outs. Sanchez is often daring hitters to swing and hit the ball, and that comes with the inherent danger that they will spot some sort of pattern in his pitching or that they will, um, really hit the ball.
But despite the fears that Sanchez’s profile initially sparked, his swerving 94 mph primary offering probably makes him better equipped than most to face the difficult task ahead.
. . .
Zach Crizer is a featured writer at Beyond the Box Score. You can follow him on Twitter at @zcrizer.