Trent Thornton looks to fill a middle reliever role for Mariners in 2024

Matt Brash's elbow inflammation and Jackson Kowar's Tommy John has underlined the importance of a guy like Trent Thornton in Seattle's bullpen, a guy who can keep hitters off base, avoid barrels, and give you innings in the middle of the pen throughout the season.
Trent Thornton, Rangers v Seattle Mariners
Trent Thornton, Rangers v Seattle Mariners / Steph Chambers/GettyImages

With the recent signing of Ryne Stanek, Trent Thornton figures to slot as the fourth righty in this pen behind closer Andres Munoz, and the high-leverage righties, Gregory Santos and Stanek. Thornton agreed to a 1YR/$1.2M deal with the Mariners to avoid arbitration back in January and has no minor league options left, which put him in a great position to win a bullpen spot in spring training from the get-go.

Now that we've seen an injury to Matt Brash, the Mariners will certainly need Thornton in this bullpen, and he may end up with an even larger role if there are any more injuries in the bullpen as the season unfolds. He pitched to the tune of a 2.01 ERA last season in 27 games, with an attractive 4.3% barrel rate and an attractive slider that generated some swing and miss in its comeback season.

Thornton had thrown the slider back in 2019 at a 27.1% clip, and its 8.7-inch vertical movement helped to project it as a plus pitch. Fast forward to 2022, and Thornton threw his four seam 41.7% of the time, and his sweeper 38% of the time.

The re-introduction of his slider resulted in 9.6 usage last year, while he also diversified his repertoire by using his sinker more. The results were encouraging, with a drop in walk rate from 9% to 4.8%, and a rise in K rate from 19.6% to 20.8%. Trent is known for his sweeper, which had a .237 batting average against in 2023, but also sported a rather dominant .172 xBA indicative of future success.

As a few fans have pointed out this spring training, Carlos Vargas is a lottery ticket type arm with closing stuff if he can throw strikes, so we'll see if he can harness his stuff (60-grade fastball, 55-grade slider, and 30 command) in the Mariners' lab. Austin Voth, on the other hand, doesn't have the dominant stuff and pitches more like a swingman/ spot starter type with a plus slider.

Thornton has more MLB success than both, with more command than Vargas and better stuff than Voth. Though Trent isn't going to show you a 30% K rate like Matt Brash, he has three plus pitches and projects well going forward. ZIPS projects a 4.04 ERA in 62 innings of work for Thornton, who can be a nice source of consistent innings for a club that's already down a few bullets and needs guys to step up.