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Seam-shifted wake and the evolution of pitch design

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Cutting edge research on pitch movement has come a long way in recent years. Let’s dive in with a new primer.

An official Rawlings Major League Baseball for the 2020 Major League Baseball season. Photo by Tim Clayton/Corbis via Getty Images

Baseball has gone through many changes over the past decade, but no element of the game has been so radically transformed as the fine art of pitching. The game is still the game, but the methods by which pitchers develop, the way they’re coached, and the statistics and data by which they’re evaluated by teams, media, and fans alike have undergone a rapid evolution over the last 10 years.

Of course, some of this evolution dates back much further. The early sabermetric era produced some fundamental insights that laid the foundation for what was to come as early as the late 90’s. As teams became more and more focused on the FIP components, pitchers who racked up strikeouts and prevented home runs became more and more attractive as compared to efficient, “pitch to contact” types.

That perspective only sharpened as we entered the era of spin data with the advent of the Trackman system and MLB’s Statcast. Quickly, we learned that whiffs are correlated to velocity and to movement. My initial simplistic assumption that high spin equals more movement equals more strikeouts was shared by a lot of the early front offices pioneering the use of that information. But then you had to consider that sinkers and changeups all have some backspin, and for a pitch with backspin to drop more than normal, you needed less backspin than average.

So there you go, the solution was simple. Go buy up all the undervalued high spin pitchers you could find, and as a backup plan, any extremely low spin pitchers as well. Any major deviation from average seemed like it could be a good thing.

Early adopters of the importance of spin data were joined by an influx of coaches and front office analysts as these insights were backed up by ever more detailed information. Raw rpms quickly became a sought after item among advanced teams. The ability to spin the ball at higher rates than other pitchers was quickly identified as one of the most attractive attributes a pitcher could possess. That insight led to sweeping changes in scouting at all levels of the game. The smartest teams in the room, such as the Tampa Bay Rays, Houston Astros, and Los Angeles Dodgers, quickly adapted their evaluations to emphasize pitchers who could spin the heck out of the ball. The rest have been playing catchup over the past few seasons.

Meanwhile, pioneering research by teams and innovators like Driveline Baseball and others quickly took their understanding far beyond raw spin. Many teams are still struggling to catch up and make use of all this new information, even as the gathering and study of it has become ubiquitous.

Magnus effect vs. gyro spin

When we first think about the relationship between spin and movement, we’re thinking about the Magnus effect. A curveball has topspin, so it moves toward the ground. A four-seamer has backspin that keeps the pitch fighting gravity and riding through the zone. Sidespin on a two-seam fastball makes the ball tail to the pitcher’s arm side. This changes if you drop your release to sidearm or submarine, but you get the drift. Specifically, the Magnus effect describes the fact that a spinning sphere will move in the direction that the spin on the front of the ball is moving.

When teams first started collecting spin rate data on a grand scale, the Magnus effect was really all they were thinking about. Presumably, the faster the spin, the more movement you’d create. To be clear, there are obviously many, many unrelated factors that go into making a good pitcher, but these early insights immediately had a profound effect on how early adopters at the college and pro levels evaluated and taught players.

High spin guys suddenly saw their stock boosted at all levels. They were encouraged to throw their best stuff more often and instructed to dial in their breaking balls. Low spin pitchers saw their stock drop a bit and were encouraged to work on their changeup as the only salvation possible. Particularly as more and more teams lacking the necessary expertise got on the bandwagon in 2016-2017, there were success stories but also widespread misapplication in the ways the new data informed their understanding of pitching.

However, by this point early research from Driveline Baseball and other cutting-edge theorists with far more experience than most teams had already quickly illustrated that the Magnus effect didn’t explain pitch movement alone. Several other factors were involved.

As they discovered, of the types of spin that are interacting on the ball’s path through the air, gyro spin, which is more like football or rifle spin, can actually inhibit movement on pitches typically designed to be affected most by high spin rpm, particularly four-seam fastballs and curveballs. Active spin, which is spin that contributes to the pitch’s movement via the Magnus effect, as opposed to gyro spin, which does not, began to be expressed with the term spin efficiency.

For a quick visualization exercise, imagine a spinning ball moving toward home plate, and it has a stick through the center that is perpendicular to the direction it’s moving. So in this example, it’s sticking out to both sides. You can hold both ends of the stick and rotate it like a steering wheel. That changes the direction that the Magnus effect will move the ball — but whether it be topspin, backspin, or sidespin, all will have highly active spin on the pitch.

Now, hold the two ends of the stick and move one side forward and the other back like steering a motorcycle. By doing so, you’ve introduced gyrospin, reducing the active spin involved. Most pitches have some of both, but initially pitchers were trying to reduce gyro to get the most Magnus effect movement possible. But as it turns out, gyro works too if you know what you’re doing.

Seam-shifted wake

The first well-known experiment to really put seam alignment into effect was Trevor Bauer’s creation of a two-seam fastball variant he called the “Laminar Express.” Essentially, recognizing that the seams create drag, Bauer tried to orient the seams on this pitch so that one side of the ball was smooth throughout its flight, and the side he wanted it to move toward had more seam involved. By doing so, he hoped to get more arm side run on the pitch as seen below.

For pitches that are designed to take maximum effect of the Magnus force, you don’t want gyrospin involved. You want the most active spin possible to maximize the Magnus effect on the pitch. This tends to apply to four-seam fastballs and curveballs most specifically. Gyrospin inhibits the Magnus effect, and yet can, with the proper seam alignments on the ball, actually create tons of movement as well — movement that may bring sinkers and changeups in particular back into prominence.

This is where Utah State University Professor Barton Smith’s conception of seam-shifted wake enters the picture. It should be noted that plenty of other luminaries, like Tom Tango at Statcast, or Harry Pavlidis, editor-in-chief at Baseball Prospectus, were all aware that active spin wasn’t explaining movement fully. And obviously the research done by Driveline Baseball most notably has driven all this evolution in the first place. There were plenty of people studying the subject, but Smith, a professor of mechanical and aerospace engineering, was able to do the actual research that uncovered much of this, and he coined the term, seam-shifted wake.

The issue, as in Bauer’s “laminar express,” is the seams. Obviously, the baseball is not perfectly round. Beyond the vagaries of baseball construction, which have come under enormous scrutiny because of the “juiced” baseball controversy, the seams create drag. Individual pitchers and coaches have understood vaguely that seam alignment can affect movement all along of course, but this was largely anecdotal, just a matter of trial and error.

It’s always been reported by hitters that some pitchers have weird late movement, for example, and spin rates, spin axis, and spin efficiency couldn’t account for it. The famous story of Mariano Rivera throwing a cutter accidentally while just playing catch, eliciting shock from his throwing partner as it dove away from his glove late, is presumably an example of a pitcher stumbling across the seam-shifting effect that can make a ball move in ways its spin would not lead you to predict.

Here’s a seam-shifted wake pitch from Dustin May. It’s been nicknamed the “Demon Sinker.” Despite modest amounts of raw spin and poor active spin on the ball, the thing moves like crazy. The effect is featured in Dan Straily’s changeup below the May clip as well.

Essentially, by adjusting grips and release to put more of a ball’s stitching spinning on one side of the ball rather than the other, there are particular alignments that make the ball move dramatically more or less than the Magnus effect could explain, depending on how the spin and drag interact.

Pitchers have always understood that scuffing one side of the baseball, or loading it with extra weight from saliva, pine tar, or other forms of tampering, could produce some unique effects. Now, all those “trick pitch” effects are becoming better understood and studied scientifically rather than anecdotally. Seam-shifting can do similar things for a pitcher, but without breaking the rules. However, it’s a subtle art to put into practice and no doubt we’re only at the beginning.

Rob Friedman, better known as the Pitching Ninja on Twitter and Youtube, has been a great public promoter of all this new research over the last few years. About a year ago, as this concept was first starting to get discussed, he put together a quick primer that should explain things better with some visuals.

Professor Smith was recently a guest on the Pitching Ninja podcast and explained most of the concepts in a longer conversation with a few visual aids. It’s well worth your time and is embedded below. You can also visit his site, Baseball Aerodynamics, to read through the experiments he’s conducting and the data he’s gathered. The quick one-sentence takeaway is that they’re beginning to understand, in a much finer way, how the subtle interaction of velocity, spin rate, spin axis and direction, seam alignments, and release all work together to make a pitch move more or less, or even in more than one direction on its path to the plate. Smith actually has a new post up with an explanation of some of the terminology and debates over usage as well. Sort of an in-progress glossary of terms and explanation.

We haven’t gotten to factoring in barometric pressure on the field and wind direction, but I’m sure that’s not far behind either. I’m only partly kidding.

On that podcast they also delve into the fact that slightly wobbling axes and/or particular seam alignments and gyrospin could make the ball move multiple ways on its path to the plate. Hitters have discussed seeing this effect forever, but much like the curveball’s movement was once thought by some to be an illusion, pitches that demonstrated late movement in a different direction from the pitch’s initial trajectory seemed to have been creatures born from illusion (excepting knuckleballs, of course). That holy grail of pitching — late movement, sometimes not even in the same direction as the initial spin movement — is now understood as being caused by seam-shifted effects. Ultimately, the utter lack of spin on a knuckleball brings seam-shifted wake effects fully into play and explains why a knuckler can often move in multiple directions on its way to the plate.

Magnus effect movement, particularly on high active spin pitches, is consistent on the path to the catcher’s glove. A curveball with high active spin dives in the same direction throughout the pitch. A pitch with more gyro, and the proper seam alignments, may start moving one way, and then as gyro re-aligns the seams in relation to the direction the pitch is moving, drag may occur on the seams that cause it to move in a different direction, or more exaggeratedly in the same direction it was already breaking toward.

Hitters learn to predict spin movement by seeing how the pitcher released the ball. Pitches that move contrary to the visual spin pattern a hitter can see from home plate can really confound the hitter’s predictive ability.

How does this matter to the Tigers?

Well, obviously, this matters to everyone in baseball. The concept of seam-shifting opens a new paradigm for the two-seamer, sinkers, and changeups in particular, but may ultimately be brought into play with any pitch that doesn’t have high amounts of active spin. Presumably even the high active spin pitches can be tweaked a bit with the seam-shifted wake concept. Generally speaking though, gyro is the friend of seam-shifted effects, and the effects are more pronounced with pitches with plenty of it.

The difficulty in knowing how much this will change pitching, is that each pitcher is slightly unique. Not only do you have to find the sweet spot with the seams to enhance these effects, you’ve still got to repeat pitches the exact same way out of the same release point while locating effectively to different spots. In other words, as a pitcher you still have most of the problems you always had.

Command, velocity, mentality, durability, reading hitters, are all just as important as ever. But especially for guys who don’t spin the ball all that well to begin with, this new understanding opens up a whole new world of potential improvements to their stuff.

A key example Dr. Smith has cited among Tigers pitchers is Spencer Turnbull’s four-seam fastball. The pitch has always been odd because Turnbull gets more than average spin rate on it and yet the amount of movement it gets has always been reported as below average by Trackman. There was no explanation of why it’s such a devastating, though erratic, pitch that is rarely barreled up for a home run and tends to get sinker-type results off the bat. Our friends over at Motor City Bengals have a clip from Smith’s appearance on their podcast recently with a quick explainer on Turnbull.

As it turns out, the seam-shifted wake effect is in play here too. The pitch was initially described in Statcast’s methodology as having poor movement, because tracking systems only measured how much a pitch moved from its starting trajectory to the glove. It couldn’t consider that it might be changing break along the way to the plate. Just in the past week, Statcast has released a whole new spin direction leaderboard that is now taking this all into account. In Turnbull’s case, it starts out moving like a normal four-seamer, but because it has plenty of gyro and the right seam alignments, it appears to cut and take off vertically as it gets to the plate. As Tigers radio color commentator Jim Price would describe it: “late movement, baby.”

This is part of why many of us are particularly excited about new Detroit Tigers pitching coach Chris Fetter. Fetter is someone who follows all this research with keen interest, has experience putting these concepts into practice, and can tailor and sell them to his players. Obviously, there is much more to coaching pitchers than the subtleties of pitch design, but other than major league experience, Fetter appears to check all the other boxes. Where he’s thought to be on the cutting edge is in translating pitch shaping research into actionable information that his pitchers can put to work.

The advantages of having a cutting edge pitching coach in this regard are pretty clear. Most teams are still out there hunting down and paying premiums for guys with the highest spin four-seamers and breaking balls they can get their hands on. These are still new, and poorly understood concepts around the game. There’s an opportunity to be ahead of the game for once, both in how and where in the draft the club drafts pitchers, and in how they teach and develop them. Fetter and others in the organization with this knowledge are the reason.

As we become more familiar with how to put the new Statcast reported spin direction data to work, we’ll begin analyzing Tigers pitchers with seam-shifted wake pitches in mind. At this point, it’s still rather unclear how well pitchers are going to be able to take advantage of these concepts, and whether or not this is going to radically alter how pitchers are evaluated in terms of the draft, trades, or free agent signings. For now, take a look at some of the embedded video, get generally familiar, ask questions in the comments below, and we’ll revisit this soon. Good luck hitters.