What is ‘seam-shifted wake’ and which pitchers benefit most from it?

Baseball had a choice, at one point. What would the ball be like? Hard, soft, or full of fish?

No joke. In the mid nineteenth century, pitchers often made their own balls and the sort-of-spheres were made of melted down shoe soles — or sturgeon eyes, in some cases — and they looked more like lemon peels than today’s horseshoes. Then came a period in which teams made their own balls; some were lively, some were deadened, and nothing was very standard. Then either Ellis Drake or Colonel William A. Cutler developed the horse-shoe design, and by the end of the 19th century, the size and shape and makeup of the ball had largely stabilized to what we know today.

That choice had a tremendous impact on the game today. We’ve already seen in the last five years what a minute difference in the seams can mean for how the ball travels when it’s hit, but now we’re starting to get a better sense of what the seams can mean for pitches.

Maybe we’ve always known intuitively that the seams are meaningful for movement. Pitchers cycle through approach as they try to find the right combination of spin, arm slot, and grip to produce the movement they are looking for. Dan Straily once tried more than a baker’s dozen changeup grips before he produced a pitch that had some of the most vertical movement in the game.

Earlier research into spin and pitch movement focused on the Magnus Effect, mostly, while also factoring in that drag and gravity factor to slow the ball down and pull it downward. The Magnus force deflects the ball depending on the velocity, spin axis, and spin rate and basically deflects it in the direction of the spin, depending on how well the spin axis and trajectory are lined up.

A highly spin efficient ball, like an over-the-top four seamer, would have spin that goes from the bottom of the ball to the top, and that creates a Magnus force that lifts the ball and creates what we call “ride” or “jump” — the ball ends up higher at the plate than the batter expects. You can see this with a beach ball if you throw it while keeping your hand perfectly behind the ball and perpendicular to the ground. Here’s a video that shows the Magnus Effect with that sort of spin, but on a lighter object, so it in fact ends up going upward.

Eventually, researchers noticed that not all balls behaved in the way that these forces would explain alone. Barton Smith, a professor of mechanical and aerospace engineering at Utah State University, started to map the wake pitches created as they flew through the air. Here’s a pitch that has Magnus force, and you can see the wake is shifted down at the top. This ball has an upward force on it, as Smith details in his crib notes on the subject.

Here’s another pitch spinning similarly, but with the seams in a different orientation. Note how the wake is different. This has a downward force upon it, as the wake shows.

This has to do with how the seams change the wake, a phenomenon that Smith has called “seam-shifted wake” and detailed on his website extensively. You can also see a deep dive on Baseball Prospectus and many videos on Youtube about the phenomenon, which was made possible by Smith’s lab setup. Now, because Hawke-Eye directly measures spin instead of inferring it from movement as Trackman did in the past — allowing us to more accurately talk about things like spin-mirroring and seam-shifted wake — we can look at which sorts of pitchers benefit from the seam-shifted wake in the big leagues.

To that end, professor of electrical engineering and computer science at the University of California, Irvine Glenn Healey, tried to separate out each of the measurable forces on the baseball so that only the seam-shifted effect would remain. He found that the effect was largest on sinkers and changeups — the two pitches in baseball that have seen the largest drop in usage over the last few years, coincidentally — and provided a list of pitchers that saw the most “side-force” effect in 2020.

One of those players was Spencer Turnbull, who might have the best fastballs to help illustrate the effect seam-shifted wake can have. Turnbull throws a four-seamer and a two-seamer that have the same spin axis on BaseballSavant’s new spin axis illustrator. They don’t move the same, at all, and that provides some deception to the hitter. Here, Turnbull throws the four-seam (red) and the two-seam (orange) to a similar starting location, but where the two pitches end up befuddles Christian Yelich.

Same axis, close to the same velos, similar spin rates — very different movement. That’s at the heart of the seam shifted wake phenomenon. The velocity and associated spin rate provide the gas, the arm slot and therefore the spin axis provides the particular road the pitch will take, and maybe the seams are the steering wheel that allow the driver to off-road if they know what they are doing.

But what can it do for you?

Well, if you’re a pitcher, it’s obvious — you’ll want to get a high-speed camera and cycle through some grips on your sinker and change until you see the seams in the right orientations to produce this effect. A good pitching coach and a direct line to Smith might help — it certainly helped reliever Jared Hughes revamp his sinker and land a job when he contacted the professor and tried to better understand his seam-shifted wake sinker.

For the rest of us, it’s possible that it’ll help us understand why pitchers like Lance Lynn, Kyle Hendricks, Brandon Woodruff, and Zach Britton (whose sinker grip is pictured below) are so good. It looks like the Cubs are all over these freshly explained phenomena, because their newest find, Alec Mills, showed up as perfectly mirroring the spin on his fastball and curveball, and also shows as having a seam-shifted wake sinker.

Britton’s unique sinker grip produces outsized movement. (Eno Sarris)

It’s also possible that existing “stuff” metrics don’t capture the excellence of these pitches. When Ethan Moore looked at the most important physical features of a pitch, he found that vertical movement and velocity dwarfed the effect of horizontal movement. But when you look at the outcomes of seam-shifted wake changeups and sinker (as defined by Healey’s list), you see that these pitches do better than the general population, without having better velo or drop, as a group.

The seam-shifted pitches had almost the exact same velocity and vertical movement as the overall population, but they had more horizontal movement, and they got more whiffs and they allowed fewer big hits. Maybe throwing a pitch where the movement deviates significantly from the spin axis is a sort of deception for hitters that sometimes report being able to see the spin axis.

Amazing! And none of this would have been possible if baseball, nearly two hundred years ago, had picked a harder ball (with fish eyes inside) that was more like the one they use in cricket.

Let’s look at some lesser-known pitchers who benefit from the seam-shifted wake.

Frankie Montas

The book on Frankie Montas as a prospect was that he threw hard, but the fact that he was extremely over the top in his delivery would limit his ability to get sideways movement, and perhaps frustrate his search for a third pitch like a changeup. For a while, that was the case, as Montas threw a four-seamer (with good vertical movement) and a slider (with good vertical movement) and looked like he might be headed to the pen. Much of his breakout was focused on adding a split-finger, which gave him a third pitch, but along the way Montas also made another significant change.

Montas started throwing a sinker, and it had some wiggle! In terms of side-to-side movement, the new sinker has a foot of horizontal difference from his slider, and five inches more arm-side fade than his four-seam. His vertical release point is unchanged from five years ago, the spin rates on his fastballs differ by only 100 RPM, and yet here he has a functional sinker that has fueled his rise as a starter. Seam-shifted wake can create movement that looks like it comes from a different arm slot, which is one way to define deception.

So what happened last year? For some reason, the spin on his fastballs declined relative to the league, from the 76th percentile to the 59th percentile, and declines like that can be related to health. Coincidentally, Montas had back problems in mid-August, and it took until late September to regain his velocity and spin rates and slider movement again. He struck out 23 in 15.1 innings to finish the season and should be considered a Top 50 pitcher going into the 2021 season.

Corbin Burnes

There might not be a pitcher in baseball that has undergone as drastic a pitch mix change as Corbin Burnes. In 2019, he threw his four-seamer and slider over 80 percent of the time. In 2020, he threw his sinker and cutter over 70 percent of the time by the end of the year. For his career, Burnes has given up 14 homers off of the four-seam and just two on the sinker. Even if you adjust for how often he’s thrown each pitch, the sinker has given up a third of the homers. Seems like an easy choice.

It’s simple when you say it that way, but it’s also more complicated. Burnes’ sinker drops almost three inches less than the average sinker, so it doesn’t look amazing as a pitch if you focus on just velocity and movement. Moore’s Quality of Stuff metric has it as the 147th-best sinker thrown in baseball last year. But perhaps the seam-shifted wake effect makes it play up?

Then there’s the command piece. Overall, Burnes has well below-average command. But among his pitches, he commands the cutter the best (league average rate by Command+), and voila, more cutter usage. Then, you look at the spin mirroring on his cutter, and it mirrors exactly with his sinker (183 degree difference). Boom, seam-shifted wake and spin mirroring helping a player that seemed on his way to the bullpen become an important piece for the Brewers’ starting rotation, and easily a Top 50 pitcher overall.

Pablo López

Here’s our first seam-shifted wake changeup on the list, so let’s take a gander.

That’s a good video because of the center field view, and also because he struck Hanser Alberto out twice that game on the changeup, and Alberto had the tenth-best strikeout rate in baseball last year.

So López has a great changeup. What should he do with it? Throw it some more, of course! He’s upped the usage from under twenty percent of the time to nearly thirty percent of the time in the last three years, and the results have come with that alteration in the mix. His search for a breaking ball is still underway, and meaningful of course, but the cutter he threw last year looked like it might be good enough to keep hitters off balance. López looks like a back end Top 60 pitcher who may outperform his projections due to the deception (and volume) on his changeup.

Brad Keller

The disconnect between what Brad Keller has done and what he’s projected to do is fairly amazing. He’s thrown 360+ innings to the tune of a 3.50 ERA and a 1.28 WHIP, and yet he’s projected to have a 4.81 ERA by Steamer next year, with a 1.48 WHIP. Knowledge of how those systems work will point you to his strikeout and walk rates — largely important to projections because the ball in play data has much more noise in it — and with a strikeout-minus-walk rate that’s far below average, maybe it makes sense.

But Keller might be one of the pitchers most affected by seam-shifted wake, according to Smith. Let’s take a look at his four-seam, sinker, and slider through the lens of his spin directions on the pitches, and the movement outcomes.

These aren’t maybe as tightly tunneled as the Turnbull fastballs, but you can see how he takes advantage of his movement to different quadrants of the zone. He has the same spin axis on his fastballs, and they have different movement. Plus, the seam shifted wake on his slider makes it have a power curve type profile, with four inches more drop than your average slider, but hard curveball velocity at 86 mph.

While Jace Peterson fouled off two of these pitches, maybe that’s kind of the point with Keller. Only three pitchers — Hyun-Jin Ryu, Max Fried, and Sonny Gray — had 100 balls in play last year and allowed batters a lower Barrel rate than Keller did. And the bottom of the Barrel leaderboard is chock full of seam-shifted wake throwers: Keller, Justus Sheffield, López, Hendricks, Dylan Bundy, Lynn, Logan Webb, Adrian Houser, Johnny Cueto, and Turnbull showed up in the best forty by Barrel rate allowed last year, in that order.

Maybe it’s not all about the strikeout.

Justus Sheffield

Oh hey look at who was right behind Keller in Barrels allowed. Sheffield’s had quite the journey from the Futures Game, where he had to field my questions about improving his curveball in the Yankees organization, to two years in Seattle that have seen some wild swings in pitch mix.

At this point, his 83 mph slurve is getting great results (18 percent whiffs, above average even if you compare to sliders) and doesn’t seem to be the problem any more. And maybe the fastball thing is solved too — he went from using the four-seam 48 percent of the time to using it one percent of the time last year. He replaced all those four seamers with sinkers, and it’s a nice sinker, too. To wit:

Sheffield doesn’t have the strikeout and whiff rates to project all that well, but if this sinker can ride the seams to some power suppression, he could be underrated by those traditional numbers. And maybe there’s untapped potential, considering how rarely he threw the four-seam last year. If he could take advantage of the seam-shifted wake effect fully, by throwing both four-seams and two-seams and playing the two pitches off of each other, then he might be able to unlock a few more strikeouts along the way.

(Top photo: Kevork Djansezian/Getty Images)