Why this Mariners bullpen option is poised for a surprise breakout

Seattle Mariners fans weren't necessarily nervous when the bullpen took over in games last year, but the unit didn't inspire quite as much confidence as the rotation. It only had one Andrés Muñoz, after all.

Better things should be in store for the relief corps in 2025. Gregory Santos is healthy after missing most of last season with lat and biceps injuries. And sometime in the opening weeks of the season, Matt Brash and his obliterating stuff will be back at manager Dan Wilson's disposal. Brash missed all of last year recovering from Tommy John surgery.

Yet with Seth Martinez now out of the picture, there is suddenly an opportunity for an unusual suspect to make Seattle's pen. To this end, consider this your notice to keep an eye on Casey Legumina.

Casey Legumina's form should look familiar

The proverbial needle didn't move much when the Mariners acquired Legumina from the Cincinnati Reds for cash in early February. A 27-year-old with 6.95 ERA in the majors? Yeah, there's not normally much to see with guys like that.

Legumina did have a pretty good season in the minors last year, however. He worked as a multi-inning fireman for Triple-A Louisville, making 39 appearances that covered 58.1 innings. His ERA was 3.24, and he fanned 57 batters against 18 walks.

The righty's ability to hit the strike zone certainly fits in with how the Mariners approach pitching. "Dominate the Zone" is their whole thing, and finishing last season with 47 fewer walks than any other team certainly gives them license to boast about it.

As for why else the Mariners were interested in Legumina, Ryan Divish of the Seattle Times may have tipped the team's hand when he observed that he throws a lot like former Mariner Paul Sewald:

Mariners fans will remember Sewald, who posted a 2.88 ERA in parts of three seasons with Seattle before going to the Arizona Diamondbacks in a surprise trade at the 2023 deadline. And at least some Mariners fans may know Sewald as a poster boy for vertical approach angle. He uses a lower release point to hack his fastball into playing faster than its low-90s velocity.

Even before the Mariners got to show him off in the Cactus League, it was apparent that Legumina was cut from the same cloth. It's how he got a solid 23.7 whiff rate on his fastball in the minors last year despite only averaging 93.4 mph on it.

“It’s not like a crazy induced vertical break pitch, but I get a lot more height visually because of that arm angle," Legumina told Kate Preusser of Lookout Landing.

Cut to now, and there's Legumina with five successful outings to show for his spring. He's pitched five innings, allowing four hits with no walks and four strikeouts. Even better, his average fastball is up to 93.9 mph and he's been mixing in more sweepers to pair with his slider.

A bullpen spot is Legumina's to lose

It was no surprise when Divish left Legumina off his projections for the Mariners' Opening Day roster in February. Even as recently as March 15, Daniel Kramer of MLB.com did the same.

Yet after Martinez got reclaimed off waivers by the Miami Marlins, RosterResource has Legumina as the next man up for Seattle's bullpen. It's possible that this will only be the case until Brash returns, but that need not be the end for Legumina as a Mariner. He has a minor league option left.

There's also the more exciting possibility, which is that Legumina continues to impress Wilson and the Mariners brass long enough to stick around for good. If that happens, it'll be because the team will have proved that its success with Sewald was no fluke. He may be gone, but Legumina can prove that his model for success is still valid.