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Pitchers can highlight their skills in many ways. Velocity and spin, release point, tunneling, command and control, sequencing and reading a batter’s body language; pitchers can squeeze out their absolute best selves with using any or all of these tools to get batters out. But there’s one substantial thing they can’t control. Luck.
What even is luck? When a pitcher throws whatever it is they want to throw as close to their desired location, their control over the situation quickly evaporates. The batter is then in charge of their own destiny. From a pitcher’s perspective, this is where luck comes into play.
In many people’s eyes, Dallas Keuchel relies on luck whenever he toes the rubber. His three strikeouts in three starts with the Minnesota Twins exemplify his nature as a pitcher. He pitches to contact and hopes for the best.
Keuchel has made an excellent career out of pitching to contact. He won AL Cy Young in 2015 and was voted an All-Star in 2015 and 2017. He has undoubtedly had help from his defense along the way, as he’s never surpassed a 23.7% strikeout rate in any season of his 12 year career. However, there is another almost mystical factor that has assisted Keuchel over the years that counters the viewpoint that Keuchel is lucky.
Just a few years ago, the term “seam-shifted wake” may not have been a familiar one to even the most elite pitchers, coaches, and cutting-edge baseball researchers. Today, the once-believed optical illusion and “God-given ability” of late movement is becoming comprehensible.
Driveline Baseball describes a seam-shifted wake as “a baseball traveling one way at first, only to change direction at some point between the pitcher’s hand and the catcher’s glove.” Smooth objects cannot experience such a phenomenon, but the seams of a baseball open the door to the movement profiles we know and love in addition to seam-shifted wake. Sliders, curveballs, even high-spin fastballs as pitchers “pull” down on the seams to accomplish more backspin.
As Driveline put it, the way a baseball cuts through the air is similar to a duck swimming in water. Being that we’re talking about Minnesota’s baseball team here, imagine a loon. The wake that the loon creates is a fine depiction of what happens to the air when a baseball passes through. If it is traveling straight, the wake on each side will be symmetrical. If that loon had a floatie on its right wing, its wake would be anything but symmetrical.
Depending on the orientation of the seams of that baseball, the wake will be different. More specifically, the flow on each side of the ball will be different. Even more specifically, one side of the wake may experience laminar flow while the other side experiences turbulent flow. Laminar flow is smooth, while turbulent flow is chaotic and rough.
The turbulent flow “sticks to the ball longer” than the laminar flow, causing one side to be pulled/pushed. It is this asymmetry that causes the sought-after late-movement that scouts, coaches, and players have chased for over a century. Below is an image depicting the seams of a baseball creating rapid downward movement, but the principles remain the same.
Utah State University’s Barton Smith, a professor of mechanical and aerospace engineering, created the graphic above. Smith has spearheaded much of the research on seam-shifted wake. You can find more of his work and findings here.
Had Keuchel been in his prime when baseball researchers discovered seam-shifted wake, he could have been a poster child of seam-shifted wake. His one-seam grip uses this attribute, causing the late movement that makes it difficult for batters to square up the baseball.
Dallas Keuchel, Sinker grip.**
[**Pretty sure…I’ll let @kidkeuchy tell me if I’m wrong] pic.twitter.com/MBUX3uTz76
— Rob Friedman (@PitchingNinja) February 6, 2018
As Driveline outlines in its article, the amount of seam-shifted wake a pitcher achieves can be inferred by the difference between a pitch’s spin-based movement and its observed movement. Keuchel’s sinker has spin-based movement at 10:30 (315 degrees). His observed movement is 9:30 (285 degrees).
Therefore, his 2D Axis Deviation, as Driveline refers to it, is 30 degrees. This number indicates Keuchel’s sinker has significantly more arm-side and downward movement than what is expected, For example the seam-shifted wake Keuchel throws with has a large role in its movement. Driveline reported in 2020 that the average 2D Axis Deviation of sinkers was just 17.6 degrees.
Having a better 2D Axis Deviation is meaningful. A graph stolen from Driveline illustrates how many more runs were saved based on a pitch’s Axis Deviation below.
Driveline’s numbers help explain the movement on Keuchel’s stuff. Like most of his career, his sinker has been difficult to hit. Keuchel has a career 58.3% groundball rate with his sinker returning rates of 62.9% or higher every year since 2018. The pitch isn’t invincible. Although it’s challenging to hit, it is a pitch made to get hit, but weakly and in a way that’s easy to field.
Keuchel’s command of his sinker (and cutter, for that matter) remains 12 years in to his career. Against lefties, Keuchel can run his sinker inside to return foul balls. His cutter accomplishes the same feat against righties, greatly helping him get to two-strike counts that, theoretically, will help him strike batters out. Keuchel is able to execute an east-west approach very well with these two pitches.\n
Unfortunately for Keuchel, his changeup and slider are not the dominant pitches they used to be from 2015 to 2018. He was once able to generate whiffs on 35-45% of swings, both pitches have struggled to eclipse 30%. In his three starts with the Twins, the whiff rate on his changeup is a paltry 17.6%. He will never be a high-strikeout pitcher, but three strikeouts in 13 innings is not a recipe for success. Some of Keuchel’s sinkers will get hit hard or in the gaps between defenders. He does have a .314 xBA and .347 xwOBA, after all.
Keuchel’s latest start against the Pittsburgh Pirates is an example of this. Of the 17 balls that Pittsburgh’s batters put into play, 16 of them became outs. Besides a Bryan Reynolds’ double that found grass, some of the outs Keuchel generated had high hit probabilities, like a 35% hit probability grounder off of Andrew McCutchen’s bat or a 65% hit probability liner off of Liover Pegeuro’s.
Until the changeup and slider come around, Keuchel will be a volatile arm. His bizarro sinker and superb command will carry him in some outings, and he’s not far from being a key contributor on a playoff team.
(h/t to Andrew Wilson for helping me understand seam-shifted wake and flow.)
More must-reads:
- Braves use explosive offense to beat Guardians in clash of MLB titans
- Nationals two-time All-Star lands on IL amid struggles
- The 'Active MLB strikeout leaders' quiz
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