Alexis Díaz Has a Unicorn Fastball

It’s not crazy to see someone make the jump from a great reliever to an elite reliever. Every year, there are a handful of stellar relief seasons that we simply just did not see coming. I was a fan of Alexis Díaz after his stellar 2022 debut (1.84 ERA, 3.32 FIP, 32.5 K%), but I did not expect him to be this dominant, as he’s taken big steps forward in more or less every stat. What’s behind it?

When it comes to pitching development, it’s important to be unique; you don’t want to look like or throw like anybody else. If you’re going to be elite, you must find what makes you special and lean into it. For Díaz, his outlier skill is his ability to release the ball closer to the plate than anybody in the world from an unorthodox angle. He doesn’t have overwhelming velocity, yet his four-seamer is one of the best in the game, and the extension is a huge reason for it. It’s as if the ball is being shot at you from a little league distance by a softball pitching machine.

Here’s how Díaz’s release point compares to other pitchers with comparable extension:

Focusing first on release point, you’ll see that none of the other four pitchers in this small cohort gets their arm as low as the Reds closer. Combine this with top-tier extension and consistently being up in the zone, and you have the explanation for how Díaz’s Vertical Approach Angle (VAA) is so flat compared to those on this list. Horizontally speaking, only Jordan Romano is as far toward the third baseline, but Díaz’s low slot arm angle is very different for hitters compared to Romano’s. In terms of spin axis, only Devin Williams is somewhat close to Díaz. The other three pitchers are more over the top. From a pitch design perspective, that would be ideal for building the perfect four-seamer, but as you can see, being different is exactly how Díaz has been successful.

Stepping away from extension as the main benchmark and pivoting to vertical release point, it becomes even clearer than Díaz is in a league of his own. Nick Sandlin, Paul Sewald, and Seth Martinez are the only other overhand pitchers who have such a low arm slot, but none of them compete with Díaz’s 100th percentile extension. On top of that, they all throw their fastballs in the low-90s rather than Díaz’s mid-90s. (Perhaps not coincidentally, the best comparison for his release point is his brother Edwin.)

When it comes to evaluating pitchers, it’s important to lay out how the pitcher is unique through the lens of numbers and measurements. But what is equally important is seeing the sequencing in a live at-bat. As a two-pitch pitcher, Díaz isn’t surprising hitters all that much; you either get the heater or the slider. But it’s still important to move your two pitches around the zone to set them up, and that’s exactly what I want to show you. I’ll start with an at-bat against the reigning NL MVP, Paul Goldschmidt.

Pitch 1 (0-0 count, 4-seamer)

Pitch 2 (0-1 count, 4-seamer)

Pitch 3 (0-2 count, slider)

Pitch 4 (1-2 count, slider)

Pitch 5 (2-2 count, slider)

This is what I call carving up a hitter. After starting with a painted four-seamer inside, Díaz follows up with a heater right down Broadway. These types of whiffs are perfectly representative of how special his fastball is; Díaz has the upper hand against elite hitters even when he challenges them in the heart of the zone because it’s not a pitch you’re accustomed to seeing.

Now that he’s ahead in the count, Díaz could go even higher with a four-seamer or change speeds with a slider. He opted for three consecutive sliders. The first buckled Goldschmidt, and while you may think of this as a backed-up slider, Díaz routinely gets these types of takes inside against righties because the pitch tunnels so well with his four-seamer. After wasting the 1–2 offering, the next slider was in the zone, and Goldschmidt had no chance.

Now let’s pivot to an at-bat against the left-handed hitting Christian Yelich:

Pitch 1 (0-0 count, 4-seamer)

Pitch 2 (1-0 count, 4-seamer)

Pitch 3 (1-1 count, 4-seamer)

Pitch 4 (2-1 count, slider)

Pitch 5 (2-2 count, 4-seamer)

Luke Maile may not have been setting up on in the inner third, but it’s clear that is where Díaz wanted to live against Yelich. He missed two fastballs just inside to start the at-bat and on 1–1 but went down the heart of the plate in between; Yelich didn’t look comfortable on any of those pitches. Then on 2–1, Díaz got a chase and whiff on a slider below the zone. Getting a hitter to expand when they are ahead in the count on a breaking ball is not an easy task, let alone a hitter with a 76th percentile chase rate. With a 2–2 count, Díaz once again found himself in the driver’s seat and went back to the fastball, fooling Yelich with a sizzling four-seamer on the low-inside corner. With a low release point and extremely flat VAA, called strikes in this location can be common if a pitcher can spot it here. It’s one reason why Díaz is so effective against left-handed hitters.

As we gear up for the second half of the season, the Reds will need Díaz to continue his dominance if they hope to hold up their playoff chances. Consistently winning close games will be crucial for a team relying on a lineup full of rookies. Luckily for them, he has proven he is well equipped to handle the ninth and carve up the heart of any team’s lineup. If you’re going to bet on anybody to close games for you during a playoff push, you can’t go wrong a Díaz brother.