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Spencer Turnbull and seam-shifted wake

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Statcast’s new spin direction leaderboard sheds some light on Turnbull’s distinctive pair of fastballs.

Detroit Tigers v. Minnesota Twins Photo by Brace Hemmelgarn/MLB Photos via Getty Images

It can feel a bit overwhelming keeping up with all of the changes in pitching data, metrics, and terminology over the past five years. Seam-shifted wake and spin mirroring are now well on their way to being regularly used terms, like spin rate or tunneling. Get used to hearing about wobbly splitters, one-seam sinkers and gyroballs in the years to come. Also prepare for a lot of these concepts and terms to be misapplied for a while until broadcasters and others better understand what’s going on.

If you missed our recent seam-shifted wake primer, we’ll try and give a quick rundown before we take a look at Spencer Turnbull and then the Tigers newest major league addition to their pitching staff, right-hander Jose Ureña.

Essentially, since the advent of publicly available spin data in 2015, pitchers and coaches have been focused on developing active spin, i.e. spin that contributes to movement, while limiting gyrospin, which on its own doesn’t necessarily produce movement. But spin data still couldn’t explain the actual movement of many pitches, as has become clear with better tracking technology like the new Hawkeye system and the rise of high speed camera usage.

Enter seam-shifted wake, the understanding that seam alignments can create drag on different sides of the ball and in the process, produce movement that the ball’s spin rate, axis, and velocity wouldn’t predict, particularly with pitches that feature higher degrees of gyrospin. In some cases, it can even cause a ball to change its movement during its flight path to the plate. Since hitters predict the ball’s path to the strike zone largely on their reaction to the ball’s spin axis and velocity out of a pitcher’s hand, seam-shifted wake confounds their expectations and confuses their predictive ability.

We still don’t exactly know what effect this new paradigm is going to have on the game, only that it’s going to be substantial. Specifically for pitches that typically feature less active spin, such as sinkers and changeups, this is a game-changer. Pitchers dependent on those offerings have been seriously devalued as teams pursued high spin, high active spin pitchers over the last half decade. Now they have an entirely new toolkit at their disposal to produce effective movement. However, even pitchers with a lot of active spin may take advantage of this to produce unique effects or to amplify the movement they already get on a pitch.

For fans, seam-shifted wake need not be something to think a whole lot about just yet. It’s hard to know how much impact it will have on run prevention. Some pitchers will get better, some pitchers may not, the same as it ever was. The reasons and terminology may be new, but there are many factors that go into good pitching, and while results follow from process, as fans we’re still most interested in results. Still, just give into it. We’ll have fun.

So far, I’m still not real confident predicting improvements for specific pitchers. The general sense is that pitching coaches and teams with the best grasp of the seam-shifted wake concept will be well positioned to move improve pitchers who don’t spin the ball particularly well. Perhaps the effects will be notable with some pitchers, but not enough overall to make a huge difference in run prevention league wide. Or, who knows, maybe everyone experiments wildly with their grips all spring and we see an absolute freakshow in 2021 that leaves hitters on their knees.

So before we try to predict what the Tigers might do with someone who isn’t consciously putting the concept into practice already, or suggest pitchers they could target in trade or free agency based on the concept, let’s take a look at the Tigers starter who most obviously embodies the advantages of seam-shifted movement, Spencer Turnbull.

Spencer Turnbull’s seam-shifted fastballs

Since spin data became available, and the concept of spin efficiency, i.e. active spin vs. inactive spin that doesn’t contribute to spin-based movement, the Tigers right-hander has stood out as a particularly interesting specimen for his pair of fastballs. Turnbull’s sinker has always graded as having above average movement both vertically and horizontally according to Statcast’s charting, while the four-seamer has always graded as well below average in both. Yet the four-seamer has an above average spin rate around 2500 rpms, and is obviously pretty effective as evidenced by the fact that it’s so rarely hit for a home run. It does get hit hard fairly regularly, but typically its on the ground or on a line rather than flying out over the fences.

Indeed, home run prevention has been the defining strength of Turnbull’s game all the way through his minor league path to the majors. In 2020, he was once again among the best in the game, registering the third lowest HR/9 mark among pitchers with at least 50 innings thrown. So in this case, we’re thinking about seam-shifted wake to explain something we already know is true. That’s still quite a different beast than looking at current pitchers with home run problems—we’re looking right at you, Matt Boyd—and figuring out how to use the concept to improve in that regard.

Take a look at this overlay produced by Eno Sarris of The Athletic. Sarris has been the best popular disseminator of new ideas in pitching for years, and while they require a subscription—worth it in our opinion—he has a good piece up on their site right now taking a look at a variety of interesting seam-shifted wake pitches.

You can get a pretty good idea of why Turnbull’s fastballs are so effective right there. Despite mediocre command and a lot of inconsistency, the big right-hander is hard to barrel up for precisely this reason. Both pitches spin on nearly the same axis, but the two pitches move dramatically in different directions on their way to the plate. In both cases, they’re benefitting from seam-shifted wake effects. Neither moves the way the spin predicts they should, and even worse for hitters, the two pitches look the same coming out of his hand and then diverge to a huge degree, making it guesswork from hitters trying to get the sweet spot of the bat on the ball.

Spin-based Movement vs. Observed Movement

Recently, Statcast began producing a searchable spin direction function. This allows us to see what the spin axis looks like for each pitch, as spin-based movement, and compare to the actual observed movement of the pitches via the Hawkeye tracking system, which replaced Trackman over the past year.

As you seen below, Turnbull’s four-seam fastball and his sinker look very similar to the hitter. The spin-based movement, which expresses how the pitch should move based on active spin, is quite different than the actual movement on the right. Both are from the pitcher’s point-of-view, for reference.

As you see, the spin axis on his four-seam and his sinker are very similar, so the two offerings look very similar out of the hand, but the actual, observed movement on the two pitches diverges substantially, as the actual clip in Sarris’s tweet shows. That divergence makes the two pitches extremely deceptive and can blow a fuse in the hitter’s predictive computer. Not only does the sinker move far more horizontally than the spin would lead a hitter to predict, but the four-seamer shows notable seam-shifted wake movement as well, getting less tailing action than expected, and even cutting at times.

Now, Turnbull has always had these home run suppression characteristics, so he came to this on his own. With Fetter on board, you can be sure Turnbull and the other Tigers pitchers are going to have more detailed knowledge and information to work from now, but he may be one of the pitchers least able to really take much more from seam-shifted wake.

Instead, let’s briefly take a look at the Tigers sole major league pitching acquisition thus far this offseason, right-hander Jose Ureña, and try and use the same information to try and predict what the Tigers might have in mind for him.

Ureña’s key weaknesses are a lack of strikeouts, and a propensity to giving up an average or slightly above average number of home runs. He’s probably not going to become a real strikeout artist at this point in his career, as his slider is a pretty average pitch. However, if he could improve a bit in that regard, and limit home runs a little more, you might have a solid mid-rotation caliber starting pitcher.

To improve in the home run prevention department, let’s look at his two fastball types. Note first that Ureña throws a lot more sinkers—42.4 percent of his pitches in 2020—and only in 2020 has started approaching 20 percent in his four-seam usage after sitting below 10 percent four-seamers in the previous few seasons.

What really stands out is the fact that, even more than Turnbull, Ureña’s two fastball types have very similar, and quite consistent, spin axes. There is pretty clearly some seam-shifted movement on the sinker that gives it the huge horizontal break—or tailing action to his armside—that Ureña is known for. Meanwhile, the four-seamer moves much more predictably with high active spin, but at a low enough spin rate—just 2161 rpms in 2020—that it doesn’t really move that well compared to other high active spin four-seamers on the vertical plane, though it does get above average horizontal movement.

The fact that Ureña increased his four-seam usage in 2020 may already be telling as an attempt to take some pressure off the sinker. If the Tigers can find something in the seam alignment of his four-seam grip and release to make it move more like Turnbull’s four-seamer, and diverge more substantially from his sinker, they might make him a lot tougher to square up. Easy for us to suggest, presumably difficult to put into practice.

Ureña is still a very hard-thrower, averaging 95.6 mph on his four-seamer in 2020. He’s generally managed to keep the walks in check as well, though 2020 was a down year in that regard. If the two fastball types become harder to barrel up by confounding the batter’s eye, and if he can be even just a little more effective with his slider, you’d have him pretty well optimized in terms of movement, and you’d probably have a league average or better starting pitcher.

Can the Tigers pull something like this off without diminishing his command? Is Ureña open enough to the ideas that he’ll be willing to experiment? That’s where a coach’s ability to build trust and explain complicated concepts in actionable ways comes into effect. Potentially there’s a lot more going on that we can tell from the available data, so it’s also entirely possible that Fetter might have a very different plan in mind. For now, we’ll have to wait and see.

Hopefully, these two examples can serve as basic starting points for readers in understanding the possibilities implicit in the seam-shifted wake paradigm, and in how to use the spin direction charting. The availability of the spin direction data is going to open up a host of new ideas to public analysts in general, but the seam-shifted wake paradigm in particular is just starting to make an impact. Watching how teams use this information is going to be very interesting to watch in the coming years.