Erik Swanson figured it out

When the Mariners traded James Paxton to the Yankees, Erik Swanson was the high-floor part of the return. And yet, through his first three partial seasons with Seattle, he looked like he might not even achieve “useful” status, racking up a 5.44 ERA and a 5.38 FIP over 100 innings between 2019 and 2021. But something’s happened in 2022: the Fargo native is suddenly striking out more than a third of the batters he’s faced and hardly walking anyone. Among the 247 pitchers who’ve thrown at least 20 innings in relief this year, Swanson ranks fifth in K%-BB%, at 30.6%, right behind Josh Hader. It’s actually a very fun top ten.

How did he do it? It started in 2020 and 2021, when he adjusted his pitch mix. When he first arrived in 2019, he was throwing his four-seamer more than two-thirds of the time. It’s not uncommon for a pitcher to rely on his fastball in his first tour of the bigs, and it made all the more sense for Swanson, since it’s long been his best pitch. The distinguishing feature of Swanson’s four-seamer is that he throws it with almost perfect backspin, creating 99% spin efficiency. If you’re new to pitch spin, backspin is a good thing on a four-seamer because it doesn’t drop on the way to the plate as much as a hitter expects. Particularly when located up in the zone, this’ll cause hitters to swing under the pitch, like this:

But mortal pitchers can’t thrive on one pitch alone, and hitters were feasting on Swanson’s fastballs, particularly when he missed his spots. When he first came up, he was complementing his four-seamer with a slider and a show-me changeup. The slider was below average, but serviceable. But the changeup was bad.

Ideally, your secondary pitches complement your fastball in some way, like by spinning in the opposite direction. It made sense for Swanson to develop a changeup, since it should have made a nice pairing with his fastball. Changeups are supposed to drop on the way to the plate—the difference between the changeup falling out from under a hitter and the fastball appearing to rise as much as Swanson’s does should have left batters bumpuzzled. The only problem was that Swanson couldn’t get his changeup to drop. It fell just 24 inches on the way to the plate, 18% less than average, and creating just 11 inches of separation between it and his main offering. Opposing hitters touched it up for a .361 wOBA. And even worse, it wasn’t creating the contrast to get the most out of his fastball.

By 2020, Swanson had dropped that dropper for a different pitch, one designed to serve much the same purpose: a splitter, which he started throwing in earnest in 2021. Where Swanson could only get 24 inches of drop on his changeup, his splitter got 33. Having found a better secondary, he started relying on it more, dropping his fastball usage from 67.2% in 2019 to 60% in 2021. It got his bad contact under control, but his strikeout-minus-walk rate was still around where it had been before, at just 17.4%.

Now, in 2022, he’s finally getting the most out of his arsenal. While he’s lost a little velocity on his four-seamer, he’s commanding it better than ever, keeping it out of the bottom of the zone. Now hitters are getting fastballs up, splitters low to the glove side and sliders low to the arm side. Here’s his 2021 pitch chart by location.

Look at all that red in the bottom half of the zone. Now check out his 2022 chart:

This is how it’s supposed to work. Hitters simply have no idea where to put their swings with the fastball defying gravity, the bottom falling out of the splitter, and the slider giving hitters just one more thing to think about. The splitter is setting up his fastball better than his changeup did and now that he’s commanding his fastball, he’s getting the most out of it. That confidence is letting him go to his fastball just 54% of the time, increasing hitters’ guess work. Check out how all the pitches work together when he battles Michael Brantley, one of the hardest hitters to strike out in today’s game. He starts by getting Brantley to swing under the four-seamer:

And he eventually puts Brantley away by getting him to swing over the top of the splitter:

Fastball up/offspeed down is hardly a revolutionary idea, but it’s one thing to have a good idea and another thing to execute it. Erik Swanson is finally executing—to one of the best whiff-rates in baseball and an ERA under 1.00. When Lookout Landing ran its 40 in 40 series in 2021, Erik Swanson was forgotten and had to get a makeup piece, befitting his fringe place on the roster. But if he keeps pitching like this, I doubt that’ll happen next year.