Rubbing Mud: 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:

• Release Differential: How far apart a pitcher’s release point is on consecutive pitches, in inches. The difference tends to be small (in an absolute sense), but the larger it is, the more likely the pitcher is using a slightly different arm slot, a different hand position, or altered arm speed to make the second pitch, (perhaps) helping a batter differentiate one pitch from another. (It’s also important to repeat a release point, simply from the perspectives of throwing strikes and avoiding injury.)
• Tunnel Differential: The distance between consecutive pitches when they reach the point at which a batter must make a decision about whether, where, and how to swing. Smaller is better, generally, since it’s less likely that the batter will be able to tell two pitches apart if that’s the case.
• Flight-Time Differential: The difference in the amount of time taken by two consecutive pitches to go from the pitcher’s hand to the tunnel point. There are positives and negatives to having a big flight-time differential. If the point of a given pitch is to deceive the batter—say, to make it impossible to tell a changeup from a fastball—then maybe smaller is better. On the other hand, the smaller this figure is by the tunneling point, the smaller the total difference in flight time will be when the ball reaches the plate. Sometimes, it might be better to let the velocity separation happen, because more velocity separation between fastball and changeup tends to lead to a higher swing-and-miss rate. Greg Maddux, the Newton of tunneling, always let hitters fool themselves when it came to speed. He was concerned mostly with throwing the ball so that it looked the same to them, in terms of his release point, the trajectory, and the position of the ball through the decision point.
• Post-Tunnel Break: The amount of break created by spin on the ball between the tunnel/decision point and home plate. More, of course, is better, since the batter has already committed himself to something by then. However, a good hitter facing a pitcher with loose tunnels is going to diagnose the pitch by that decision point, and their swing will be aimed at the place where they expect that late break to take the ball.
• Plate DIfferential: How far apart consecutive pitches are when they cross home plate. This is the total amount of separation between where one pitch ends up (outside corner, at the knees) and where the next one ends up (off the plate, in the dirt, perhaps), in inches.
• Release:Tunnel: The ratio of the differential between release points to the differential between positions at the tunneling point. Generally speaking, the smaller this number is, the less information the batter has gotten with which to tell that one pitch is not the same as the last.
• Break:Tunnel: The ratio of the amount of break after the tunnel point to the differential between positions at the tunneling point. A big number usually means that the batter either faced a very small differential with which to distinguish pitches at the tunneling point, or got a good-sized differential but then had to deal with a lot of late movement. Either one is a good thing, so bigger is better.

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.

(If you haven’t already, you simply must read Jeff Long’s piece on the slider from last week. A lot of the insights he shares there add valuable dimension to the thoughts above.)

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:

1. Isn’t it fun how different these numbers are from the ones in the changeup and slider tables? It’s a good reminder of how many different looks a pitcher with a deep repertoire can give a batter, and of how different the objectives of different pitch interactions can be.
2. I wouldn’t put a lot of stock in Release:Tunnel for curveballs. See how it’s a smaller number than any above, even though the median tunnel differential is wider than for any of the other pitch pairs? I’m pretty sure that reflects the tendency for some pitchers to release the curve such that it has a hump in its trajectory out of their hand, as the spin takes hold and shapes the ball’s path. That won’t show up as either an exaggerated release differential or a wider tunnel differential, but you’d better believe batters can spot it in the pitchers who do it that way.

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:

“What I have never understood about ground ball pitchers, and do not understand now, is why they always get hurt. Show me an extreme ground ball pitcher, a guy with a terrific ground ball rate, and I’ll show you a guy who is going to be good for two years and then get hurt.”

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.