September 19, 2017
The Sinker Doesn't Play Well With Others
Earlier this month, Jeff Sullivan of FanGraphs wrote about a global trend in pitching throughout MLB. Pitchers are throwing fewer fastballs (as a percentage of total pitches) than ever before, at least for the decade during which we have reliable data. What Sullivan found is that, while it’s true when considering fastballs as an undifferentiated set, it really doesn’t capture the whole truth. He looked at Pitch Info, which (correctly) tags four-seam and two-seam fastballs (the latter often being called, and being called from here onward in this piece, sinkers) as separate pitches, and found that the loss of fastballs is almost all sinkers.
The league is increasingly selecting for pitchers who use four-seam heat to work up in the zone, frustrating batters’ efforts to attack the ball on an uphill plane and get it in the air—or at least, that’s the theory Sullivan puts forward for the shift. I mostly agree. There’s no doubt in my mind that the move toward four-seamers and away from sinkers is at least partially in response to batters making changes geared toward handling those sinkers, and punishing them. (Recall that, as recently as 2013-2014, Ray Searage’s Pirates were at the cutting edge of run prevention because they so consistently pounded hitters with sinkers that ran in on their hands or nipped the bottom of the strike zone; there has been ample incentive for batters to adjust in turn.)
However, I see at least a couple of other reasons why sinkers are disappearing league-wide, even as four-seamers largely maintain their standing as the official primary pitch of baseball, in this era of such highly evolved combat between batters and pitchers. The way the sinker interacts (or fails to interact) with other pitches in pitchers’ arsenals and our changing understanding of the factors that lead to elbow injuries are helping drive the league toward more four-seam fastballs, and fewer sinkers.
To illustrate the first of these things, let’s undertake an exercise in pitch tunneling. (If the concept isn’t already familiar, you can re-read the introductory information about it here.) The gist is that, with modern pitch-tracking data, we can map the entire flight of every pitch, from the pitcher’s hand to the catcher’s mitt. That allows us to analyze the ability of a pitcher to repeat their release point, from one pitch to the next, and it allows us to quantify the differentiation between consecutive pitches in terms of their flight path at certain points. Because the batter can’t track the ball all the way to home plate with his eyes, and has to make a decision as to whether and how to swing when the ball is scarcely halfway home, knowing this information allows us to tell how well pitchers disguise their offerings.
This season, 81 pitchers have used a [four-seam fastball, changeup] sequence at least 50 times. Below, I list the median hurler (40 guys have higher values, 40 have lower ones) for those sequences in each of our key tunneling metrics. Here’s a very quick rehash of those metrics, and their meaning:
Median Pitch Tunneling Values, Four-Seam Fastball-to-Changeup, 2017
For the moment, just let the table above be what it is. Now, let’s take a look at the median players and values among the 47 pitchers who have thrown at least 40 [sinker, changeup] sequences this season.
Median Pitch Tunneling Values, Sinker-to-Changeup, 2017
On average, pitchers who throw both a sinker and a changeup tend to be more able to make them look the same out of their hands than pitchers who throw a four-seamer and a changeup. (There are, of course, pitchers who throw all three pitches, and we’ll get there shortly.) Batters will usually have a harder time telling whether a pitch is a given hurler’s sinker or his changeup than whether it’s another guy’s four-seamer or his changeup.
On the other hand, look at the late break, plate differential, and Break:Tunnel numbers. If you’re even a part-time student of pitching, this is probably unsurprising. In general, sinkers and changeups behave the same way. They’ll tend to run to the arm side. They’ll tend to sink. Many pitchers seem comfortable throwing both pitches, which is probably because they require such similar arm action and can be thrown from the same slot and position on the rubber without an attendant problem pitching to certain parts of the zone. Unless one of the offerings is an outlier in some way, though—maybe the changeup has an unusual amount of cutting action, or the sinker is more of a true two-seamer with a lot of tail but very little sink—they move so similarly that they don’t end up fooling many batters.
Rather, they might fool batters, but those batters might still end up making solid contact, because the speed and ultimate location of the two pitches just might not be disparate enough to avoid that. Four-seamers better set up good changeups to induce swinging strikes, which is (as we well know by now) at the top of any pitcher’s wish list every time he winds up. Okay, you say, but changeups aren’t the only secondary pitch with which one need concern oneself. In fact, when you think of sinker-ballers, you tend to think of the old saw: “He’s a sinker-slider guy.” So, let’s repeat that exercise, with sliders. Ninety-seven guys have thrown [four-seamer, slider] at least 65 times this year.
Median Pitch Tunneling Values, Four-Seamer-to-Slider, 2017
Sixty-one pitchers have gone [sinker, slider] at least 45 times.
Median Pitch Tunneling Values, Sinker-to-Slider, 2017
These numbers almost don’t make sense. The median plate differential is almost the same for the two pitch pairs. The sinker again provides a smaller median release and tunnel differential, and the flight time differential is smaller, but again, the post-tunnel break is radically different, and it skews the most important number of all (the bottom one, Break:Tunnel) in the four-seamer’s favor.
Because we only express the absolute differentials (for now), the reason for this hides in the data a bit. From a scout’s perspective, the difference would be easy to see and express: it’s two-plane break. More specifically, it’s two-plane break differential, in this case. A four-seamer and a slider are going to diverge considerably on the vertical plane, and a little on the horizontal plane. A sinker and a slider are usually going to diverge very little vertically, but a whole lot horizontally. The latter is easier to pick up, and (while more likely to generate ground balls or weak contact, at least until hitters start engineering swings to go down and lift pitches like those) less likely to induce swings and misses.
Hell, we’re here, let’s do curveballs. Seventy-seven pitchers have thrown [four-seamer, curve] at least 50 times.
Median Pitch Tunneling Values, Four-Seamer-to-Curveball, 2017
Before we get into sinkers, two things:
Forty-one pitchers have thrown [sinker, curve] at least 40 times this year.
Median Pitch Tunneling Values, Sinker-to-Curveball, 2017
Nothing here is terribly surprising. Curveballs are ground-ball pitches for a lot of guys who otherwise throw four-seamers and work up in the zone, but most guys who lean on sinkers already have a ground-ball pitch (their sinker). There’s also (again, a scouting thing here, not in the data) a tendency for pitchers with lower arm slots to throw sinkers and sliders, and for guys with higher ones to throw four-seamers and curves. It’s just a bit more natural.
The Value and Cost of Independence
Obviously, the sinker still has a strong foothold in the game today. That isn’t going to change. There will always be sinker-ballers, and some of them will be very, very good. The reason the sinker is not as popular as it was even a few years ago, however, is simply that it doesn’t go well with other pitches, and most pitchers need multiple pitches in order to dominate opposing hitters. That might be truer than ever before, and if it is, then it’s probably also true that the times have never been harder for sinker-ballers.
I’ll offer this other idea, too. Four-and-a-half years ago, in March of 2013, Bill James wrote an article on his site called “The Analogy of the Fisherman.” It was about the long-held conventional wisdom that ground-ball pitchers are better than others, and about James’ belief that this conventional wisdom was backward. At the time, James wrote this:
I think I’ve come up with one possible reason. (It’s a good time to revisit the question, by the way, since Zach Britton and Dallas Keuchel are the latest super-sinker slingers to be beset by injury issues.) Let’s say, for the sake of argument, that what I laid out above is true, and that sinkers don’t set up other pitches well. If that’s true, the only guys using sinkers on a regular basis (and remaining good enough to pop up on our radar, as fans) are going to be the ones who throw almost nothing but sinkers, and have such a great one that they can succeed that way.
Britton is the top example. Jeurys Familia is another notable one. Remember when Kendall Graveman started this season suddenly throwing an upper-90s sinker almost 90 percent of the time, only to have his great run interrupted by injuries? That’s the problem, and it might be why James observed so many guys who leaned on sinkers blowing out. Throwing hard, and especially throwing hard a large percentage of the time, is a contributor to injury risk, especially to a pitcher’s elbow.
Mike Sonne’s Fatigue Units for pitchers factor in the percentage of their pitches that are fastballs, as well as their average fastball velocity. Throwing the sinker over and over, inducing grounders and working deep into games, isn’t the panacea it might seem to be. Pitchers are mixing their pitches more than ever, both to keep opposing batters from sitting on any particular offering (because any batter can railroad any pitch if he’s sitting on it, these days) and to protect their arms. The sinker doesn’t play well with other pitches, so increasingly, it’s being left out.