On the always developing concept of seam-shifted wake

I’ve been trying to better understand seam-shifted wake (SSW) for a while now. Usually that comes in the form of looking at specific pitches that have the look and working my way backwards. Lucky for me, and everyone, there are some folks constantly thinking about this and attempting to better explain it. The most informative example I’ve seen thus far came last week from Baseball Prospectus’ Michael Ajeto.

Seam-shifted wake is one of those baseball concepts that isn’t all that easy to grasp. If you think of pitch movement in a binary way, although that is definitely an oversimplification, it gets a little easier to understand. The ball moves based on the spin of a pitch or the way the seams interact with the air. That’s not perfectly true, but it has helped me understand the importance that seams play when it comes to imparting movement onto a baseball. There is a much more detailed explanation of SSW though.

Ajeto explains it like this:

“Pitches with heavy SSW component create turbulence on one side of the baseball, creating force that is asymmetrical and causes unexpected movement. SSW is a way of creating movement that more commonly comes from different arm slots than the respective pitcher. To hitters, the movement is incongruent from they expect the ball to move based on its spin at release.”

Okay, that’s helpful. SSW helps to fool a batter’s eye by creating unexpected movement. You’ve seen this clip before if you read my piece on Michael King and his ability to harness the power of SSW with his repertoire, and most notably, his whirly:

This has the look I was talking about and checks off the pieces that Ajeto mentioned in asymmetrical force and a batter’s eye being deceived. We already kind of knew this though. That piece about King mentioned this deception and another piece I wrote back in February discussed spin axis deviation’s importance as a component of SSW. It’s not that I was wrong with analysis, spin deviation still matters, but I was a little misleading in how much it truly matters. Consider this note from Ajeto in regards to a graph showing magnitude of axis deviation versus a pitch’s run value.

“The graph descends just like the previous graph … but rises immediately, creating a positively skewed distribution. This means that, even tough it’s been suggested that more axis deviation is good, the graph suggests otherwise. Too little axis deviation is likely to lead to poor results, but too much axis deviation is just as bad.”

I for one, always thought more deviation equals nastier pitch. However, a SSW sweet spot exists! Too much or too little deviation is likely to have a negative effect on a pitch’s results. Ajeto goes on to explain this misconception came about due to the fact that more gyro (bullet) spin creates more deviation, and that deviation is a necessary (still important) component of SSW. It seems Goldilocks’ lesson of moderation is also applicable to SSW.

You’re probably thinking what in the world this has to do with the Yankees. I’ll tell you — it’s clear that the Yankees pitching development not only greatly understands SSW as an idea, but they also have methods in place that are mobilized to harness SSW to their pitchers’ best abilities.

For example, Aaron Boone said it himself, Clay Holmes has the best sinker in the world. Why is that? His combination of velocity, location, and pitch movement are unparalleled. In his case, that movement is mainly due to the properties of SSW. Like King, Holmes has nearly perfected his pitch mix and a big piece of that can be attributed to hitting the gyro spin and spin deviation sweet spots. Take a look at his sinker and slider, the only two pitches he has thrown this season.

Filth. In fact, they’re somehow better than last year. In Holmes’ 28 innings last year, he had a 1.61 ERA and 2.10 FIP. Both those marks have come down in his 21.2 innings this year to a 0.42 ERA and 1.57 FIP. His slight adjustments in spin active spin percentage and spin direction on his slider are the biggest reasons why.

The sinker is pretty much the same pitch in terms of spin properties. It was already nasty and didn’t need to change. Well, the slider didn’t necessarily need to change either, but it had room to be unlocked. It seems that Holmes was getting too much gyro spin on the pitch and increasing his active spin percentage to 40 percent brought him to the sweet spot Ajeto referenced.

This change helped him increase the horizontal movement on the pitch from 2.5 inches of sweep to 10.5 inches of sweep, a huge difference. I was surprised to see he hasn’t adjusted his release point on the pitch much at all, indicating to me there must be a slight grip adjustment or wrist position adjustment. Whatever he did, it’s working very well. See for yourself — the pitch’s added sweep is a game changer.

As you know, King has been nearly as dominant as Holmes, throwing even more innings. He’s got the best whirly on the pitching staff. I’ve said it before and I’ll say it again, his whirly is perhaps the nastiest breaking ball in baseball. However, the pitch I’m focused on for this exercise is King’s sinker. While the pitch has very similar tilt/spin direction as 2021, his slight adjustment in decreasing the pitch’s active spin percentage by eight percentage points has it made it an amazing called strike machine.

Two of the best hitters in the league looked so confident these pitches were balls, but the late, deceptive movement was enough to fool and freeze them. King has quite literally done this better than any other pitcher in baseball. Of all pitchers who have thrown at least 50 sinkers, King leads them all in called strike% at 37.7 percent. The next is former Yankee, Joely Rodriguez, at 36.1 percent. The clip against Vladdy is important because it shows these aren’t just takes to take. Hitters are genuinely being fooled by the pitch’s late movement.

Unfortunately, I do not have access to expected pitch movement data, but I would be confident in betting that King and Holmes would be among the league leaders in the actual movement versus expected movement differentiation. Their ability to fool and freeze hitters is what makes them so special. When I do get access to that information, I’ll be sure to share it, but for now when discussing SSW, we can take a well rounded look which includes spin deviation, active spin percentage, and video to confirm the pitch has a bit of wiffle ball in it.