The Mariners have two improved relievers for similar and different reasons

Last year, the Mariners weren’t very good. To be fair, for the past two decades, the Mariners haven’t been good. Their starting rotation was one of the better staffs in baseball, but they just didn’t have a complete roster. They had several offensive players flop, and their bullpen was the worst — literally, tied for the worst — in baseball. To improve their team in the easiest way possible, the Mariners chose the path of least resistance and completely overhauled their bullpen.

Kendall Graveman has been perhaps the most high-profile pitcher to join the Mariners bullpen. Even though he’s scuffled since returning from the COVID-19 injured list, he has the ninth-lowest ERA- of all relievers. That’s helped the Mariners’ relievers to move from dead-last in WAR in 2020 to fifth in 2021 and stabilize the backend of the bullpen. But Graveman hasn’t been the best reliever by WAR. He hasn’t been the second- or third-best either. The bulk of the production has come from the likes of Paul Sewald, Drew Steckenrider, and JT Chargois, in that order.

Before this season, you didn’t know Sewald, and you didn’t know Chargois. Usually, I’d offer a qualifier with statements like that, because I can’t know all of my readers. But be honest, you didn’t know who they were. And neither did I. Steckenrider has been around for a while, and he’s flashed some promise, but he hadn’t had a good enough career to date to earn anything more than a minor-league deal with the team in November.

The trio is all overperforming their peripherals, but Sewald and Chargois separate themselves from Steckenrider and the rest of the Mariners’ bullpen because it’s not just their outcomes, to date. Their peripherals are strong too, which suggests the possibility that they can continue to be strong relievers moving forward. By K-BB%, Sewald and Chargois have posted strong numbers at 26.6% and 26.3%, respectively.

Steckenrider is a fine middle reliever, but he doesn’t seem like someone who can handle higher-leverage situations like Sewald and Chargois might be able to be. That sounds weird, but it’s true. There’s plenty of room to fall back to earth, but Sewald and Chargois seem like a pair of effective relievers.

They share a few similarities, ones that I’ve written about before. The first is that they’ve both seen upticks in their slider usage since coming to the Mariners. It seems like one of the Mariners’ favorite tweaks. Sewald has seen his slider usage rise from 33.3% last year to 46.2% this year — he’s almost throwing it as much as his fastball. Chargois? He’s gone full Austin Adams. He’s throwing his slider 74.7% of the time, up from 58.8% when he last pitched in 2019.

The other similarity that they share is that they throw from pretty low arm slots, which generally means a lot of side-to-side movement on one’s pitches. Sewald is a perfect example of that:

If it’s not clear (and it’s probably not), this plot shows the spin direction of Sewald’s pitches paired with their respective spin rates. The closer to the center, the less spin. The closer to the outside, the more spin. You can see here that Sewald’s pitches mirror each other pretty well. On a clock face, his fastball spins at about 1:45, whereas his slider spins at 8:45. Both of his pitches get more horizontal movement than average.

Because of this, you’ll see a lot of fastballs up in the zone to his arm-side, and sliders low in the zone. Sewald doesn’t pitch east-west as much as you’d expect given his pitch characteristics, but he does some.

Chargois has a much different look:

By spin direction and spin, Chargois’ sinker looks awfully similar to Sewald’s fastball. Whereas Sewald sits at 92 mph, though, Chargois sits around 96 mph, while spinning his sinker much more efficiently. The end result is a harder sinker with much more sink and arm-side movement.

Where he really sets himself apart from Sewald is his slider. You may notice that Chargois’ slider’s spin direction is all over the place. That seems like a bad thing, but it’s not. It means that he throws a gyro slider, which means that — because his slider has almost pure gyro spin — it’s able to resist drag and move straight through space. That means that, aside from the forces of gravity, Chargois’ slider would literally not move vertically, depending on the pitch. As is typical of pitches with heavy gyro spin, its spin direction is all over the place, with some of his sliders moving to his arm-side, some to his glove-side, and some not moving horizontally or vertically. It’s the best.

Here it is in action:

It’s not an exceptional-looking pitch. You’re not going to find people posting gifs of it. But for all it lacks aesthetically and getting hitters to chase, it makes up for in efficacy. Chargois has posted a 32.3% CSW with it on the year, while using his sinker (34.2% CSW) to steal called strikes.

Now, I may have led you to believe that Sewald has a plus slider. That’s not the case. It’s fine — he’s posted a 29.9% CSW with it on the year — but where he’s different from Chargois is that his success derives from his fastball. Aside from Justin Steele — who you could justify filtering out of this search query — Sewald has the best fastball CSW in baseball. It’s unreal.

Sewald has always thrown his fastball for strikes, but never like this. What’s changed is that he’s throwing elevating his fastball to his arm-side more than ever — that’s where he gets the most swinging strikes. Of equal importance is that he’s dropped his arm slot, which has helped his fastball improve its vertical approach angle from -4.2° to -3.8°. And if you adjust for height, the difference is even starker. In other words, his fastball is entering the zone at a flatter angle, which has helped him miss more bats. Again, part of that is from dropping his arm slot, but it’s also because he’s elevated his fastball more.

Here’s Sewald getting Shohei Ohtani to whiff:

And José Ramírez to strikeout:

Sewald’s fastball doesn’t look exceptional. But the results speak for themselves. He gets both Ohtani and Ramírez to whiff on 93 mph fastballs, which has been the theme for Sewald on the year: his fastball’s swinging-strike percentage is an obscene 17.2%.

And so, Chargois and Sewald go about things in similar, but different ways. Chargois has the do-nothing slider, and Sewald has the sneaky fastball. Both pitchers take different routes to success, but in the end, they both seem like similarly compelling relievers. And for two relievers that didn’t start the year on the opening day roster, that’s awfully impressive.