Could Aaron Ashby Be the Most Important Piece of Brewers' Playoff Bullpen?

[Matthew Trueblood]

Image courtesy of © Jovanny Hernandez / Milwaukee Journal Sentinel / USA TODAY NETWORK via Imagn Images

Hitters are (finally) (sort of) getting to Aaron Ashby this month. Heavily used because of his phenomenal ability to deliver length and dominance ouf of the bullpen, Ashby is starting to show slight signs of wear in the closest thing he's had to a full big-league season since 2022. He takes great pride in sponging up innings and protecting his fellow relievers, and Pat Murphy takes great comfort in knowing that whether he needs one ground ball to escape a tight spot or seven outs to bridge the gap between a short start and the rest of his high-leverage relievers, Ashby can give it to him. That does come with a price, and thus, Ashby has run into a bit of trouble over the last week.

On the whole, though, he remains brilliant, and the team will have time to back off and let him freshen up before the National League Division Series starts in early October. Last year, he proved he could be valuable as a relief weapon. This year, he's proved he can be the relief weapon, at least for short stretches when that need arises.

Few pitchers in the league give opposing batters a tougher combination of looks than Ashby does. His sinker is averaging over 97 miles per hour this year, but it's far more than that velocity from a lefty that makes him nasty. He uses a very high arm slot, for a sinkerballer, and he releases the ball with (mostly) backspin. But the seam-shifted wake effects created by his grip and the interaction of the seams of the ball with the air creates a ton of arm-side run, relative to what any hitter will expect based on how Ashby throws.

Here, you can see the difference between the initial spin direction on his pitches and the actual direction of their movement. The way his sinker and his changeup fade away from a right-handed batter is not at all normal.

Among lefties who have thrown at least 350 sinkers this year, here are the ones whose movement direction varies most from the direction of the spin they impart on the ball at release—along with their average arm angle on sinkers.

1. Max Fried (44.8°)
2. Ranger Suárez (36°)
3. David Peterson (41.5°)
4. Framber Valdez (42.2°)
5. Ashby (49.9°)
6. Jared Koenig (35.2°)
7. Brendon Little (26.3°)
8. John King (28.7°)
9. Adrián Morejon (43.7°)
10. Angel Zerpa (26.1°)

Although his lack of extension down the mound makes it play slightly slower than it is, Ashby throws his sinker much harder than most of these fellow southpaws. He also comes from a much higher slot, where hitters tend to expect more four-seam action. Opponents expect some extra run on a fastball from an arm slot like Little's, or even Koenig's. From Ashby, it's extra funky.

Notice in that graphic, too, that the spin direction on Ashby's sinker and curveball are almost perfectly opposite one another. That creates a spin-mirroring effect, which makes it very hard for the hitter to identify the pitch early, based on spin. A spin axis rotated 90° between two given offerings will give one of them a different look as the ball rotates and the seams blur, but when it's more like 180°, the axis is functionally the same; the seams will spin in opposite directions but on the same orientation. That adds to Ashby's overall deceptiveness.

Hitters do have a different way to spot Ashby's pitches and discern them. It's the release and trajectory of them. Here's a Statcast animation of a right-handed hitter's perspective on Ashby's delivery, with the average release and trajectory of each of his pitches color-coded.

Pretty early, you can spot that the sinker is going straight and low, while the curve starts high and then snaps downward. They don't come out of the hand on the same plane and then diverge; he tends to let the curve pop a bit for a batter.

Remember, though, that the hitter isn't seeing these nice, colorized trails. They're just seeing a ball. A righty hitter, in particular, is seeing a ball that seems to come right after them, out of Ashby's hand and from his new placement on the third-base side of the rubber. Last year, the way he aligned himself and located both his sinker and his curve, he didn't make it very hard for hitters to see which pitch was coming.

The offerings ended up in similar locations last year, but to get there, they had to start on different planes out of Ashby's hand. This year, though, he's letting the sinker live a bit higher in the zone and stay out over the plate (counting on that movement-based deception to get ground balls with it, anyway), while steering the curveball ever more toward a righty's back foot.

Whatever the previous animation indicated, then, hitters are probably having a very hard time telling the sinker and the curve apart out of Ashby's hand. The angles he offers and the way the two pitches have to move to reach these destinations, they do effectively look the same to a batter. 

A lefty throwing a sinker to righties can still be dangerous, and Ashby is notably better against lefty batters. However, he's dominated this year on the basis of a repertoire and a blend of characteristics that plays no matter who's in the batter's box, or on which side of the plate. That he complements these offerings with a big-breaking slider and a changeup he's long called his "favorite pitch" makes him more than equal to facing an entire lineup, if needed. In turn, that makes him an immensely valuable bullpen piece. The 2025 Brewers don't have any other reliever who can deliver in a wider variety of must-win situations.

Milwaukee still needs to get to October healthy, and the hope is that that will mean getting Trevor Megill and/or Nick Mears back. Abner Uribe is locked into the quasi-closer role for now. Koenig is a different but important lefty option, alongside Ashby. By no means will he be the star of the poseason for the Crew—but he could steal a scene or two, as all great ensemble players eventually do.

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[Brian]

If Aaron Ashby is "on" he can be almost unhittable.  But if he has his usual control issues corralling his pitches he becomes very average if not detrimental with his walks.