Seam-Shifted Wake, Red Sox Pitchers, and You

Hairps

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TL;DR Seam-shifted wake, or side force, is the difference between a pitch’s observed spin and its measured spin, as detected by MLB’s recently-installed HawkEye systems. Players whose pitches exhibit this type of movement have become hot commodities, driven by a number of the more forward-thinking MLB clubs. It’s important because, depending on the type of pitch, the amount of seam-shifted wake has shown to be a significant contributor to a pitch’s effectiveness. Summary links to Red Sox pitchers’ seam-shifted wake leaderboards can be found towards the bottom of this post.


I’ve seen a bit of chatter in different threads about the profile of pitchers that Bloom has targeted, the emerging importance of spin rates and now seam-shifted wake among forward-thinking teams around the league, and how any of this might apply to Sox pitchers. I’ve spent some time deep down the SSW Rabbit Hole and hope that others might find this summary helpful…


What is seam-shifted wake?

When a ball spins a certain way and on a certain axis, there is an expectation for how it should move. However, with seam-shifted wake pitches, the air around the ball is being altered by the location of the seams (hence seam-shifted wake), which pushes it in an unexpected way. SSW refers to the additional side force movement caused by this. This is different than the Magnus force that lifts the ball and creates “ride” or “jump” causing the ball to go up higher at the plate than the batter expects.


Who discovered it?

Utah State Professor Barton Smith is generally credited with “discovering” seam-shifted wake. The Driveline guys are said to have been studying the issue separately as well around the same time, but still. Mostly Smith.


How is it measured?

MLB’s Mike Petriello framed up how to think about SSW as comparing a pitch’s “observed movement from spin direction at the plate with the spin-based movement out of the pitcher's hand.” Put another way, "how is the actual movement at the plate different from what the original spin direction would have suggested?" And yet another way (via Smith), what you want to look for in SSW is the deviation (difference) “between the spin direction and the actual direction the ball moved.”


Is it important?

MLB’s Tom Tango isolated the effect of SSW on different types of pitches’ run prevention and showed that SSW does, in fact, play an important role. In particular, for sinkers and cutters. Research continues. SSW seems to play some role in a slider’s effectiveness. As research continues, Smith believes that breaking balls will prove out as being impacted as well.

Diving a bit more into what Tango did -- he placed all pitches from 2020 to Mid-April of this season into three different bins. Bin 1 included the 25% of pitches with the MOST amount of movement, Bin 2 included pitches with the middle 50% of movement, and Bin 3 included the 25% of pitches with the LEAST amount of movement. He then looked at how effective each bin was at preventing runs per 100 pitches. What did he find (limiting here to just sinkers and cutters)?

Sinkers:

Total Break:

1 [most movement]. -0.22

2 [middle]. +0.08

3 [least]. +0.46


Magnus:

1 [most movement]. +0.07

2 [middle]. +0.05

3 [least]. +0.51


SSW:

1 [most movement]. -0.41

2 [middle]. +0.37

3 [least]. +0.36

Here we see that the story of the Sinker is all about the SSW (or more technically the non-Magnus force, which we are presuming is the SSW).

The sinkers that are getting the most SSW are by far the most effective.
Just to summarize what we’re seeing here -- for sinkers, those with the most SSW movement prevented runs at almost twice the rate (-0.41) as sinkers with the best overall movement (-0.22)

Cutters:

Total Break:

1 [most movement]. -0.01

2 [middle]. +0.23

3 [least]. -0.29

Magnus:

1 [most movement]. +0.13

2 [middle]. -0.32

3 [least]. +0.45

SSW:

1 [most movement]. -0.61

2 [middle]. -0.02

3 [least]. +0.58

Here, the cutters finally make sense, because of the SSW. If we just look at total break, the most effective cutters are those that have either the most or the least amount of break, with the least amount of break winning. In other words: a slow non-breaking fastball. Which is… odd.

If we look at the Magnus force splits, the conclusions are even more confusing. So, we learn nothing (or less than nothing, negative nothing) by looking at the Magnus splits of cutters.

Ah, but SSW on Cutters, that’s where it happens: by far, the cutters with the most SSW are the most effective, and those with the least amount of SSW are the least effective. Finally, we get to see some explanation for how to measure the effectiveness of cutters and it lies with the SSW.
Pretty amazing. Just look at how effective the 25% of cutters with the most amount of SSW movement are at preventing runs (-0.61) relative to the same class of pitch with different movement characteristics.


Who are some of the MLB leaders in SSW?

Savant has leaderboards that can be sorted by the “Deviation” between the spin direction and actual direction. They present them as clock units, which I don’t really dig, maybe that’s just me. RHP and LHP appear on opposite ends. Here are links for sinkers and cutters (you can run leaderboards for other pitches, but I know that this post is already long as shit):

MLB leaders in sinker SSW movement (min 25 pitches)

MLB leaders in cutter SSW movement (min. 25 pitches)


How do Red Sox pitchers’ seam-shifted pitches fare?

Here are leaderboards I created for our guys, for each of MLB’s pitch classifications:

Red Sox pitchers' 4-seamer SSW movement (min. 25 pitches)

Red Sox pitchers' sinker SSW movement (min. 25 pitches)

Red Sox pitchers' changeup SSW movement (min. 25 pitches)

Red Sox pitchers' curveball SSW movement (min. 25 pitches)

Red Sox pitchers' cutter SSW movement (min. 25 pitches)

Red Sox pitchers' splitter SSW movement (min. 25 pitches)

Red Sox pitchers' slider SSW movement (min. 25 pitches)
 

ookami7m

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There was a recent interview on the Effectively Wild Podcast about seam-shifted wake for those who may want to know more. Great post Hairps!
 

Sandy Leon Trotsky

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TL;DR Seam-shifted wake, or side force, is the difference between a pitch’s observed spin and its measured spin, as detected by MLB’s recently-installed HawkEye systems. Players whose pitches exhibit this type of movement have become hot commodities, driven by a number of the more forward-thinking MLB clubs. It’s important because, depending on the type of pitch, the amount of seam-shifted wake has shown to be a significant contributor to a pitch’s effectiveness. Summary links to Red Sox pitchers’ seam-shifted wake leaderboards can be found towards the bottom of this post.


I’ve seen a bit of chatter in different threads about the profile of pitchers that Bloom has targeted, the emerging importance of spin rates and now seam-shifted wake among forward-thinking teams around the league, and how any of this might apply to Sox pitchers. I’ve spent some time deep down the SSW Rabbit Hole and hope that others might find this summary helpful…


What is seam-shifted wake?

When a ball spins a certain way and on a certain axis, there is an expectation for how it should move. However, with seam-shifted wake pitches, the air around the ball is being altered by the location of the seams (hence seam-shifted wake), which pushes it in an unexpected way. SSW refers to the additional side force movement caused by this. This is different than the Magnus force that lifts the ball and creates “ride” or “jump” causing the ball to go up higher at the plate than the batter expects.


Who discovered it?

Utah State Professor Barton Smith is generally credited with “discovering” seam-shifted wake. The Driveline guys are said to have been studying the issue separately as well around the same time, but still. Mostly Smith.


How is it measured?

MLB’s Mike Petriello framed up how to think about SSW as comparing a pitch’s “observed movement from spin direction at the plate with the spin-based movement out of the pitcher's hand.” Put another way, "how is the actual movement at the plate different from what the original spin direction would have suggested?" And yet another way (via Smith), what you want to look for in SSW is the deviation (difference) “between the spin direction and the actual direction the ball moved.”


Is it important?

MLB’s Tom Tango isolated the effect of SSW on different types of pitches’ run prevention and showed that SSW does, in fact, play an important role. In particular, for sinkers and cutters. Research continues. SSW seems to play some role in a slider’s effectiveness. As research continues, Smith believes that breaking balls will prove out as being impacted as well.

Diving a bit more into what Tango did -- he placed all pitches from 2020 to Mid-April of this season into three different bins. Bin 1 included the 25% of pitches with the MOST amount of movement, Bin 2 included pitches with the middle 50% of movement, and Bin 3 included the 25% of pitches with the LEAST amount of movement. He then looked at how effective each bin was at preventing runs per 100 pitches. What did he find (limiting here to just sinkers and cutters)?

Sinkers:



Just to summarize what we’re seeing here -- for sinkers, those with the most SSW movement prevented runs at almost twice the rate (-0.41) as sinkers with the best overall movement (-0.22)

Cutters:



Pretty amazing. Just look at how effective the 25% of cutters with the most amount of SSW movement are at preventing runs (-0.61) relative to the same class of pitch with different movement characteristics.


Who are some of the MLB leaders in SSW?

Savant has leaderboards that can be sorted by the “Deviation” between the spin direction and actual direction. They present them as clock units, which I don’t really dig, maybe that’s just me. RHP and LHP appear on opposite ends. Here are links for sinkers and cutters (you can run leaderboards for other pitches, but I know that this post is already long as shit):

MLB leaders in sinker SSW movement (min 25 pitches)

MLB leaders in cutter SSW movement (min. 25 pitches)


How do Red Sox pitchers’ seam-shifted pitches fare?

Here are leaderboards I created for our guys, for each of MLB’s pitch classifications:

Red Sox pitchers' 4-seamer SSW movement (min. 25 pitches)

Red Sox pitchers' sinker SSW movement (min. 25 pitches)

Red Sox pitchers' changeup SSW movement (min. 25 pitches)

Red Sox pitchers' curveball SSW movement (min. 25 pitches)

Red Sox pitchers' cutter SSW movement (min. 25 pitches)

Red Sox pitchers' splitter SSW movement (min. 25 pitches)

Red Sox pitchers' slider SSW movement (min. 25 pitches)
This is amazing... but I'm also at a complete loss as to how to read this and how it applies to our pitchers.
 

StupendousMan

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Thanks very much to Hairps for a very informative opening post.

This is still a relatively new quantity, and I'm not very familiar with the details. I worry a bit about random effects showing up in the data. For example, if a wind gust happens to push the ball an inch to the left, that deviation from a predicted trajectory would -- I assume -- be assigned as due to SSW. Is that right? If the number of pitches per hurler which show significant SSW is small, then a large part of the effectiveness of these pitches might not be due to any action of the pitcher. I'll have to do some reading, but I wonder how repeatable the SSW factor is for some particular pitcher from year to year.

Should be a fun topic for the summer!
 

drbretto

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Absolutely love this post. Fascinating. It's too bad the nature of it means there's no way to look back through history with it. I'd love to see how Pedro's changeup or Mo Rivera's cutter stack up.
 

drbretto

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Do you really need to look back for that information? Pretty apparent that they'd be at the top.
If there was a way to apply this to all of baseball history, your first thought wouldn't be to go back and see if that was, indeed, the secret sauce? Or try to find a case to bring up some unsung heroes that would otherwise be lost to oblivion?

Really it's just I haven't been keeping up with baseball for a few years, so it's hard to appreciate the effect.
 

Rovin Romine

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If there was a way to apply this to all of baseball history, your first thought wouldn't be to go back and see if that was, indeed, the secret sauce? Or try to find a case to bring up some unsung heroes that would otherwise be lost to oblivion?

Really it's just I haven't been keeping up with baseball for a few years, so it's hard to appreciate the effect.
I wouldn't. This is very cool from a physical science point of view, but isn't the game-takeaway that some pitchers can throw with more movement than others? Haven't we always known that?

In a way it's like the radar gun. But prior to the gun, we knew some pitchers threw faster than others.

Movement, like speed, is just one part of the overall pitching equation, which is best measured by practical in-game results. And that's where the heroics (if they can be called that) lie.
 

ookami7m

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Thanks very much to Hairps for a very informative opening post.

This is still a relatively new quantity, and I'm not very familiar with the details. I worry a bit about random effects showing up in the data. For example, if a wind gust happens to push the ball an inch to the left, that deviation from a predicted trajectory would -- I assume -- be assigned as due to SSW. Is that right? If the number of pitches per hurler which show significant SSW is small, then a large part of the effectiveness of these pitches might not be due to any action of the pitcher. I'll have to do some reading, but I wonder how repeatable the SSW factor is for some particular pitcher from year to year.

Should be a fun topic for the summer!
This is one of the things they talked about on the EW podcast episode - there's no real way to account for a breeze swirling in the stadium - so it's just noise in the system. Figure over a large enough sample I'd imagine all of the wind effects will balance out.
 

drbretto

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I wouldn't. This is very cool from a physical science point of view, but isn't the game-takeaway that some pitchers can throw with more movement than others? Haven't we always known that?

In a way it's like the radar gun. But prior to the gun, we knew some pitchers threw faster than others.

Movement, like speed, is just one part of the overall pitching equation, which is best measured by practical in-game results. And that's where the heroics (if they can be called that) lie.
But this is isolating a particular type of movement. Isn't it? Did I misread it?

Edit: I mean, is this a new idea or no? And if so, why wouldn't you want to compare it to history?

Not that it matters, of course, because you can't anyway.

Edit 2: I mean, even if this was before and after the invention of the radar gun, you wouldn't wish you go go back and measure how how fast people were throwing? I truly am baffled by this response, lol
 
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effectivelywild

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This is amazing... but I'm also at a complete loss as to how to read this and how it applies to our pitchers.
The quick and dirty way to interpret these charts are just to look at the "deviation" column. The greater the deviation (expressed in terms of clock faces), the greater the seam-shifted wake (SSW). The columns to the left (spin-based and observed) describe the pitch movement. The "spin-based" column describes the axis upon which the ball is spinning---so if the ball is spinning with perfect backspin, the axis is 12:00. This is, incidentally, the column that is new this year. The "observed" column describes an inferred axis based on the pitch's movement. This is what we had before. The different between the two columns is deviation.

Let me give you a quick example. Take a look at Hairps' Sox 4 Seam Fastball SSW leaderboard.


Garrett Richards is at the top, with deviation of 0h45m. His four-seamer, based on the way it actually spins (12:30 axis) should have some arm side run. But his observed axis is 11:45, which means the pitch actually has some slight cutting action. That difference is attributed to SSW.


What is interesting about SSW is it adds an additional component to pitches, other than just pure movement, for us to look at to try to figure out what makes a pitch effective. This actually helps solve what I think of as the cutter conundrum---the effectiveness of cutters doesn't appear to be tied to their overall movement. But SSW seams to separate good cutters from bad ones.

Fangraphs has a good writeup of this here.

The importance of SSW appears to vary depending on the pitch type. For cutters (and sinkers), SSW (aka non-Magnus forces) is really key to their effectiveness. For four seamers, it seems like there's some sort of synergy between Magnus (spin) and SSW based movement that boosts their effectiveness. For changeups, Magnus is king. For sliders, neither seems to be particularly important. The research and numbers from Tango Tiger are here.

This stuff is cool if you like to geek out about pitch design, but there are 2 significant limitations we do run into.

1. We have some trends we can observe, but we don't really have a great understanding of why they occur. Let's take cutters for example---SSW appears to be key for their value. Why? Um, we can only speculate. And why is SSW less important for changeups? Again, we can only speculate.
2. We lack data for comparisons. We only have data for this year. So, for example, if we notice that Eduardo's cutter seems to be less effective so far in 2021 than it was in 2019 (xwOBA of .376 vs. .318), we can't determine if there is a loss of SSW that is causing this or if it is something else. Similarly, I haven't been able to use an easily accessed repository of data for this info on a pitch by pitch or even game by game basis---what I've seen on Baseball Savant is aggregated for the year (if anyone knows where I could find a more granular breakdown, please let me know). So the next time Garett Richards gets knocked around, we won't be able to see if anything about, for example, his fastball on that start has changed allowing batter's to tee off on it.

Still, it's progress in the study of trying to understand what makes pitches effective. If the Sox could make some strides in figuring out how to tweak pitches slightly to make them more effective, it would be huge. Imagine what it could do for player development and for the success of those veterans that get picked up for cheap in the hopes that they will be effective.
 

Sprowl

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I am perturbed by the decision to define seam-shifted wake entirely as side-to-side motion. If in fact some pitchers are able to generate unexpected motion by the way they grip the baseball and the resulting friction of the seams as they pass through the air, that should affect vertical motion as well. In other words, if SSW is the horizontal residual of actual ball movement on the way to the plate compared to observed spin coming out of the pitcher's hand, then there should be an additional factor (let's call it seam-shifted vertical deviation SSVD), which would be the difference between the Magnus force imparted by observed spin and the actual vertical movement of the ball relative to projectile flight.

How good are these new Hawkeye camera systems? Is there really a difference between observed spin and measured spin? How are observation and measurement different processes?
 

nvalvo

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I am perturbed by the decision to define seam-shifted wake entirely as side-to-side motion. If in fact some pitchers are able to generate unexpected motion by the way they grip the baseball and the resulting friction of the seams as they pass through the air, that should affect vertical motion as well. In other words, if SSW is the horizontal residual of actual ball movement on the way to the plate compared to observed spin coming out of the pitcher's hand, then there should be an additional factor (let's call it seam-shifted vertical deviation SSVD), which would be the difference between the Magnus force imparted by observed spin and the actual vertical movement of the ball relative to projectile flight.

How good are these new Hawkeye camera systems? Is there really a difference between observed spin and measured spin? How are observation and measurement different processes?
With the caveat that my sole qualification here is that I’ve listened to that Effectively Wild conversation with Barton Smith twice, it sounds like he agrees with you.

The key issue seems to be the relationship between the seams and the pitch tilt, and thus the interaction between grip and arm angle. But people tend to leave that out of their descriptions, because transverse/active/efficient spin gets described as “vertical” and gyro/bullet/football spin “horizontal” even when both are actually relative to the pitcher’s arm slot. (I think?)

But it also seems clear that Chaim Bloom and company are really into this stuff, even as no one actually knows how to make it work. The Richards acquisition is one datapoint, and it sounds like the Tanner Houck assortment of fastballs may be another SSW case in point. But maybe a prominent failure of the new regime is even more revealing: it sure seems like the team has been trying to turn Ryan Weber into a store brand Kyle Hendricks, without much success so far. Because lord knows what else they saw in that guy.

And it's not really observed vs. measured. It's that the old PitchFX measurement of spin took the observed path of the ball and inferred what the spin *must have been* based on a model of gravity, spin rate, and magnus forces, while the Hawkeye system uses cameras to actually observe the spin axis. For a bunch of pitchers and pitchers the systems agree. But the pitches with discrepencies are those where PitchFX system infers a different spin pattern than the one the Hawkeye system sees.

Still, it's progress in the study of trying to understand what makes pitches effective. If the Sox could make some strides in figuring out how to tweak pitches slightly to make them more effective, it would be huge. Imagine what it could do for player development and for the success of those veterans that get picked up for cheap in the hopes that they will be effective.
Piggybacking on this point, something they mentioned on your namesake podcast is that where they anticipate the biggest impact of this is in player development. For awhile teams like Houston have been selecting for pitchers with hard, high-spin four seam fastballs with high RPM and spin efficiency, and throwing them at the top of the zone. Now everybody likes those guys: Matt Barnes is going to get paid this offseason, maybe by Boston. Within that framework, SSW is bad — it's low efficiency. That's not the movement they're looking for.

So I think the application of this stuff is more about what you do with some high school pitcher you drafted in the thirteenth round who doesn't have high-90s velocity or high RPM. It's not that we're going to ask Matt Barnes to develop SSW pitches — we already know what to do with a guy like Barnes — it's that we're going to find a way to develop an effective repertoire for that ninth-rounder.

What Barton Smith said on the podcast was really cool, I thought: he said that he hoped that in five years there will be 20 guys in the majors fooling hitters while throwing 87.
 
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VORP Speed

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I wouldn't. This is very cool from a physical science point of view, but isn't the game-takeaway that some pitchers can throw with more movement than others? Haven't we always known that?

In a way it's like the radar gun. But prior to the gun, we knew some pitchers threw faster than others.

Movement, like speed, is just one part of the overall pitching equation, which is best measured by practical in-game results. And that's where the heroics (if they can be called that) lie.
In-game results really aren’t the the best measure anymore, that’s the thing. In-game results are a second-order effect. The advanced ball motion analytics are starting to provide a deeper understanding of why in-game results occur and how they can be manipulated. Look at Gerrit Cole on the Pirates vs the Astros. The Astros took his elite spin rate that was being wasted on too much horizontal movement, tweaked his spin axis to turn some of that horizontal movement into vertical movement, had him start locating higher in the zone and turned him into the best pitcher in baseball.
 

Rovin Romine

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In-game results really aren’t the the best measure anymore, that’s the thing.
As a measure of quantative data? No, "ye olde eyeball" will never stack up to tools.

But the in game results, however muddy they may be, are the only ones that matter.

Justin Masterson had an amazing sinker. It was quantitatively [pretend I have inserted math-formula for "really freaking good"]. Half of his seasons were average-or-worse. However, if you had magically given that pitch to me (in my athletic prime) to complement the rest of my pitches, I'd still have sucked more than anyone on the 2020 Sox staff. Including the position players. By several orders of suckitude. And that's how one values the actual/apparent movement of the pitch, qua actual/apparent movement.
 

StupendousMan

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It is difficult to talk about these effects when the data isn't public. Until it is made available to all, so that we can all examine it closely, all we can do is listen to the claims of those who do have access. And, as long as access requires $$, one might be suspicious of any claims that the new product will help one to identify and train more effective pitchers. "Sorry, I can't tell you any more, but if you purchase this special 3-year account for $50,000, you and your staff will be able to improve your team's ERA by 0.30 over the next five years!"
 

Hairps

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In case any of the follow-up below is of interest to others...

2. We lack data for comparisons. We only have data for this year.

Still, it's progress in the study of trying to understand what makes pitches effective. If the Sox could make some strides in figuring out how to tweak pitches slightly to make them more effective, it would be huge. Imagine what it could do for player development and for the success of those veterans that get picked up for cheap in the hopes that they will be effective.
FYI, you can also access 2020 data by changing "season", as I have on this leaderboard link.

Imagine what it could do for player development...
The Cubs, for one, have already tapped into this:
Before pitchers and catchers were due to report to spring training, Cubs pitching coach Tommy Hottovy got a phone call. It was one of his pitchers, and they briefly chatted about how the pitcher had progressed in his offseason work.

Before hanging up, the pitcher had a question for Hottovy: “Hey, how much of this ‘seam-shifted wake’ stuff are we into?”

Hottovy couldn’t help but laugh.

“Remember last year in spring training when I showed you that new grip on a pitch?” Hottovy said. “Well, what did it do?”

The pitcher remembered how the pitch moved differently, and it suddenly clicked that what he’d studied over the winter was something the team had already had him utilize. They may not have had a name for it, but the Cubs pitching infrastructure knows how to maximize movement.
https://theathletic.com/2509979/2021/04/11/what-is-seam-shifted-wake-and-why-is-it-important-to-kyle-hendricks-and-the-cubs/

Driveline is definitely doing this, and I think it's also safe to connect the dots to the Reds, as Driveline's founder, Kyle Boddy, also serves as Director of Pitching for the Reds.

...and for the success of those veterans that get picked up for cheap in the hopes that they will be effective.
Again with the Cubs:
Partly due to budget constraints — high-velocity pitchers with great breaking balls are in high demand — the Cubs targeted undervalued softer tossers this offseason. But it wasn’t strictly about money. They believed they could help maximize those pitchers’ talents, partly because they believe they know how to leverage pitchers whose arsenals boast seam-shifted wake movement.
https://theathletic.com/2509979/2021/04/11/what-is-seam-shifted-wake-and-why-is-it-important-to-kyle-hendricks-and-the-cubs/