How Taijuan Walker remade himself

An in-depth look at Walker's post-surgery pitch design

When it was first reported the Mets were signing right-hander Taijuan Walker, I did what many of you probably did at the time, and pulled up Google to search his stats. On the surface, the numbers looked good: 4-3 with a 2.70 ERA—a nice, healthy 2020 campaign after missing most of the previous two seasons due to Tommy John surgery.

But then I navigated over to Baseball Savant and was less impressed.

His fastball velocity and spin rate rank near the bottom of the league, he doesn’t strike many people out, and opponents hit him pretty hard. If we were to leave it right there, a “smart” baseball fan might say that his underlying numbers suggest his top-line performance is due for a regression.

But you probably wouldn’t be reading this newsletter if you were content to just leave it there, so let’s dig a little deeper in understanding why there is reason to believe Walker could be a useful starter for the Mets.


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Two things jumped out at me in researching the evolution of Walker’s pitch design:

  1. The location of his 4-seam fastball;

  2. His transition from relying on a cutter, as a secondary pitch, to a slider.

First, his fastball. It is Walker’s most used pitch. He threw it 38.3 percent of the time last year and held opponents to a .156 batting average against, which is more than a 100 point drop from the two seasons before his injury when he was throwing nearly 2 MPH faster. 

Think about that for a second: while his fastball velocity is slightly down since before his surgery, his results have been better. Not only did he turn more batted balls into outs, he generated more whiffs (23.1%) than he has at any point in his career in which he threw at least 200 fastballs.

What changed was where he located the pitch. Walker started living higher in the zone during the pandemic-shortened season.

While his spin rate and velocity don’t translate into anything special, by throwing his 4-seam with a high spin efficiency (maximizing the movement of the pitch by creating nearly 100% backspin) and locating it along the upper edge of the strike zone, he has found some success. Only 15 pitchers threw a 4-seamer in this upper region of the zone more consistently than Walker did last year. And on those pitches, he produced a 16.7% swinging strike rate (vs 8.6% overall).

As we have talked about before with Trevor Bauer, pitchers generally can’t change their spin rate unless they use a foreign substance. You are stuck with what you have, like a fingerprint. But you can improve spin efficiency by optimizing how you throw the ball. And you can see in the representation from Driveline below how spin efficiency on a fastball (generating lots of backspin) is important in maximizing the “rise.” Given the same characteristics, a fastball with higher efficiency will have less vertical drop (or a higher location).

In summary: while Walker lacks an impressive spin rate and has lost velocity on his fastball, by locating the pitch higher in the zone and maintaining efficiency on its backspin, he has been effective.

To complement his high fastball, Walker also changed the grip and release point on his cutter to create more depth and transform the pitch into a slider that lands low and away from right-handed hitters. This gave him something he didn’t have before Tommy John surgery, and that is two pitches that right-handed batters swing and miss at when they are properly deployed.

The concern that remains is his hard hit rate. The danger of pitching up in the zone at 92-93 MPH is that big league hitters can turn a mistake into a big fly pretty easily. And while Walker gets more whiffs along the top edge of the strike zone than he does overall, he doesn’t have the type of stuff that hitters chase, as demonstrated by a career-low 21.2% reach rate against his 4-seamer last season. So if he misses a little up, it’s likely going to be a ball; and if he misses a little down, it’s likely going to be trouble.

This is why his collection of secondary offerings is important. Besides his slider, he also throws a split-change, and perhaps most importantly, a two-seam fastball that has similar velocity to his 4-seamer, but has more drop and arm-side movement. If he can master that pitch, it should keep him out of trouble when he has difficulty locating his 4-seamer up in the zone. This is still a work in progress.

Oh, and Walker also has a curveball he isn’t afraid to throw early in the count. We will have to talk about that more in another newsletter. But if you are looking at the individual pitch metrics for Taijuan Walker and find yourself unsure of what he has to offer following Tommy John surgery, hopefully this gives you an idea.

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