Bryce Elder, Spin Doctor

Through seven starts, it’s hard to say that Bryce Elder isn’t in it for the long haul. He has a matching FIP- and xFIP- at the moment, at a gladdening 86. In other words, his pitching has been commensurate with preventing runs at a rate 14 percent better than league average, and nothing in the rate of his fly balls leaving the yard suggests anything different. That’s pretty handy for a guy who didn’t even make the rotation out of Spring Training. Elder’s 0.7 fWAR on the year ties him for the 40th-most among starters in MLB so far, and amusingly, he’s sixth among all starters in WPA.

But, quality of his pitching aside, there’s something else to talk about when it comes to Bryce Elder: seam-shifted wake. Unfortunately, if this is the first time you’re hearing the term, or you’ve heard it before but aren’t quite sure what it means, I am definitely not the right person to explain it to you. You could read some articles about it, but if you’re outcome-focused, they may not help you much. The bottom line is something like this, though be aware that this is less accurate and more instructive. For accuracy, again, see the links at the bottom of this post.

When a baseball is thrown (or struck by a bat), it moves along a certain trajectory. However, the baseball has seams, which get “caught” on the air the ball moves through. The seams cause a lot of the nuances in modern baseball — the frequency and direction of the ball’s spin relate to how the air interacts with the seams, and cause the ball to move in specific ways that are helpful (or harmful) to players trying to achieve their goals. The more-basic version of this interaction is straightforward: more spin can cause fastballs to “carry” (that is, not drop as much you’d expect) and breaking balls to plunge or skate (break) further than they otherwise would. But, seam-shifted wake is a more complex interaction, where what happens is that instead of a pitch moving the way you’d expect given the direction of its spin, something about the nature of the pitcher’s grip, arm action, release, and the like results in a deviation between how the ball should move with the spin on it, and how it does move.

Why does seam-shifted wake matter? Again, I’m not the best person to explain this. But, the general idea is that to the extent hitters rely on recognizing (largely subconsciously) spin out of the hand, and (again, probably subconsciously) alter their swings to match the expected path of the ball with a certain spin profile, if a pitch moves differently than what hitters are recognizing, what results is a misalignment between the swing used and the actual path of the ball as it moves towards the plate. (Note: this paragraph somewhat suggests that a greater difference between expected-based-on-spin-axis and actual movement is better, but I want to be clear that that’s not the case. It appears that some degree of subtlety is needed.)

As you’ve probably figured out by now, because this post is about Bryce Elder, the Braves’ young right-hander has some top-notch seam-shifted wake shenanigans going on. One way to look at this is just to take a gander at the charts on his Baseball Savant Player page:

The diagram on the left-hand side basically just tells you the spin axis of each pitch as it comes out of Elder’s hand. The right-hand side, though, tells you, based on how the pitch actually moved, what the spin axis should have been to get the movement that resulted. In other words, Elder’s sinker (orange) moves as though its spin axis was more horizontal than it actually is. Similarly, his slider (yellow) moves as though its spin axis was more vertical than it actually is. (The changeup, green, is similar to the sinker in this regard. And, much like Bruno, we don’t talk about Elder’s four-seam fastball.)

It’s hard to get a gauge of whether this sort of thing is remarkable just from a chart that only applies to Elder. After all, if everyone has some degree of seam-shifted wake, it’s possible that there’s just nothing special about the deviations above. But, since this is a post focusing on Bryce Elder, I can safely tell you that yeah, this deviation is actually quite remarkable.

Through Sunday’s games, there have been 432 pitchers that have thrown at least one pitch 50 times during the 2023 MLB season. Using Baseball Savant computations, if you average the deviation in observed versus inferred spin axis, there are only 15 with more average “spin deflection” than Elder. However, of those 15:

• Six rank highly because they only have one pitch thrown more than 50 times;
• Of the remaining nine, another six only have one pitch with spin deflection in the area of Elder’s sinker, slider, and changeup, rather than multiple such pitches; and
• Of the remaining three, only two have this type of extreme spin deflection on two pitches where the deflection goes in opposite directions, like Elder’s slider and sinker. Those two pitchers: Richard Bleier and Marcus Stroman.

Want to see an example of what I’m talking about, rather than just reading text? It’s a little hard to see in the videos, but it’s there.

This is probably the most obvious case for Elder’s sinker, but it also wasn’t a particularly competitive pitch.

This painful foul might be better:

Elder’s sinker is supposed to fade, and it does... but the seam-shifted wake gets in the way a bit.

It’s more obvious with the slider, because the seam-shifted wake gives it an almost screwball-esque quality. You can tell this from the movement charts as well as the videos.

Like Drew Smyly’s curveball of yore, sliders aren’t “supposed to” fade. Even the entire genus of “gyrosliders,” now differentiated from sweepers that twirl gloveside, still have some minimal gloveside break. But not Elder’s, which because of the seam-shifted wake, actively “backs up” relative to where and how he releases it.

You can see this double-play inducing pitch from Elder kind of “pause” as a result of seam-shifted wake.

This sequence to Tommy Edman early in the season is perhaps more illustrative. There’s a strike one slider-that-is-kind-of-like-a-curve-or-something:

And then you can see what this sort of weird motion can theoretically do to a batter on the next pitch, as Edman fails to hit the same-ish pitch squarely as a follow-up:

In theory, Elder having a sinker that doesn’t fade as much as it should, and a slider that fades at all, should be a nightmare for batters. Even without the combination of two pitches at different speeds whose movement profiles can blur into each other in an unexpected way, there’s some evidence that seam-shifted wake is helpful for sinkers in general, as shown in a chart in this article from Driveline.

And yet, with all this, that’s somehow not what we see with Elder, at least not a pitch basis. Think about all the ways in which this phenomenon could help. It could help manage contact. It could help get called strikes. Perhaps it could help best on pitches in the zone, generating weaker contact than expected on hittable pitches. All of those seem plausible, perhaps, but none are actually happening.

For one, and most obviously, Elder’s xwOBA/xERA, based on the quality of contact he allows as well as his walks and strikeouts, is his weakest ERA estimator, and the only one of his estimators (including cFIP and DRA from Baseball Prospectus) that is average-or-slightly-below. (His 4.36 xERA is the same as the league’s current ERA.) His called strike rate is marginally lower than league average (16.6 percent to 16.2 percent). The league swings at more of Elder’s in-zone sinkers and sliders than they do on average for the pitch type, and his xwOBACON on in-zone sinkers is worse than league average. If you were going to build any kind of syllogism about how this is working, at all, you’d need to heavily rely on the fact that Elder’s xwOBACON on in-zone sliders is way better than the league (.287 to .377), but Elder doesn’t throw his slider in the zone more than usual (46 percent compared to the league’s 45 percent) so it’s hard to say it’s some kind of deliberate strategy to take advantage of the sown confusion from seam-shifted wake. Plus, the real issue is that Elder’s sinker is heavily crushed (.373 xwOBA) despite an average launch angle of zero, so we can’t just say “seam-shifted wake” or “spin deflection” as an explanation for his success so far.

It’s also worth noting, in general, that Elder’s command has not been much of an asset so far, despite his lack of velocity to compensate.

The sinker has a consistent general area but bleeds into waste territory or into the middle of the plate. The slider seems to suffer from an execution issue where too many drift into the zone. Fortunately, and perhaps because of the spin deflection/etc., it’s not being hit hard, but either way, Elder isn’t executing the gloveside corner placement. The changeup is spiked more often than not. I’m still not talking about his four-seamer. Elder’s walk rate and strikeout rate are both lower than league average by about a percent, so again, no great shakes there.

Bottom line: perhaps the benefits from Elder’s excessive seam-shifted wake are what’s keeping him at an above-average pitching line despite underwhelming velocity, command, and location. If so, it could be happening based on his slider’s “ability” to avoid getting crushed, which might be because of its strange movement profile. Again, Elder certainly looks like he’ll be sticking around, so we’ll get to see how this evolves over time. But right now, he’s a specific kind of spin doctor — one that doesn’t actually seem to be benefiting all that much from what he’s doing to the ball as he lets it fly.

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For actual stuff that isn’t just me blathering about seam-shifted wake, places to start could be:

• Driveline Baseball: https://www.drivelinebaseball.com/2020/11/more-than-what-it-seams-an-introduction-to-seam-shifted-wakes-and-their-effect-on-sinkers/
• The Athletic: https://theathletic.com/2337324/2021/01/22/seam-shifted-wake-sleeper-pitchers/
• Esteban Rivera, Pinstripe Alley: https://www.pinstripealley.com/2022/5/24/23138573/yankees-pitch-movement-seam-shifted-wake-holmes-king
• Michael Ajeto, Baseball Prospectus: https://www.baseballprospectus.com/news/article/74601/climbing-the-ladder-were-talking-about-seam-shifted-wake-wrong-axis-deviation/
• Brandon Day, Bless You Boys: https://www.blessyouboys.com/2021/1/11/22167019/mlb-pitching-seam-shifted-wake-detroit-tigers-chris-fetter-sinkers