What can Mariners expect from reliever Gregory Santos?

When the Seattle Mariners traded for hard-throwing reliever Gregory Santos in February, the hope was that he would team with Matt Brash and standout closer Andrés Muñoz to create a three-headed monster in the bullpen.

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It didn’t work out that way. Brash is set to miss the entire season after undergoing Tommy John surgery, while Santos missed the first 90-plus games with a right lat strain that he suffered in spring training.

But after multiple setbacks, Santos is finally set to make his Mariners debut. Seattle activated the 24-year-old right-hander from the 60-day injured list on Monday, giving the M’s a much-needed high-leverage arm to help bridge the gap between their elite starting rotation and Muñoz.

Santos has a potentially devastating two-pitch mix, with a sinker that averaged 98.8 mph last season and an elite slider that averaged 91.4 mph, according to Baseball Savant.

“He throws really hard and he has a very good offspeed pitch,” ESPN MLB insider Jeff Passan said Tuesday on Seattle Sports’ Brock and Salk. “And that’s kind of all you need to be an effective reliever. His slider is nasty.”

During his first full season in the majors last year, Santos posted a 3.39 ERA with 66 strikeouts and 17 walks in 66 1/3 innings with the Chicago White Sox. However, the raw numbers don’t tell the full story.

Santos recorded the lowest barrel rate among any pitcher in the majors last season, with opposing hitters barreling the ball on just 1.0% of their plate appearances. He gave up just two home runs all year.

Gregory Santos strikes out the first batter he faces on Major League rehab with a 98 mph fastball pic.twitter.com/461OihBinx

— Tacoma Rainiers (@RainiersLand) July 3, 2024

Santos’ slider was particularly dominant. Opponents hit just .196 off the pitch last season, while posting a 37.5% whiff rate. They hit a grand total of one extra-base hit off his slider all year.

“He’s not Matt Brash, but he’s gonna be about as good of a facsimile of Brash as you’re gonna find, because of the velo, because he will strike guys out, because he induces weak contact,” Passan said.

“This is not a guy who’s gonna be taken deep very often. And he should be a very reliable bridge in the eighth inning to get to Andrés Muñoz, who by the way probably should’ve been an All-Star.”

Listen to the full conversation with Jeff Passan at this link or in the audio player near the top of this story. Tune in to Brock and Salk weekdays from 6 to 10 a.m. or find the podcast on the Seattle Sports app.

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