The Mariners’ top candidates for September callups

The Seattle Mariners and the rest of Major League Baseball will have some roster decisions to make in the coming days.

Is a bullpen role in Bryce Miller’s future?

MLB active rosters expand from 26 to 28 players on Sept. 1. Per the rules of September roster expansion, clubs cannot carry more than 14 pitchers but they can carry more than 14 position players. So, each team will be calling up at least one position player and could add as many as two.

Either way, the Mariners are likely to call up one position player and one pitcher, especially if they go to a six-man starting rotation that would leave the bullpen an arm short.

Below are Seattle’s top candidates for a September promotion. All stats are through Wednesday’s games.

Position players

Michael Arroyo, 2B/LF

The Mariners have struggled against left-handed pitching all year, which is something the right-handed bat of Arroyo could address. The 21 year old has put up strong numbers since being promoted to Triple-A on July 7, batting .271 with an .810 OPS, seven homers, nine doubles and one triple. But much of that production came early on, as Arroyo is hitting just .208 with a .693 OPS in 22 August games.

There are some questions as to how Arroyo would fit on the big-league roster. Most of his experience has come at second base, a position Cole Young has locked down in an everyday role. And while the M’s have given Arroyo time in left field this year, it’s still a position he’s rather green at and one that is held down by All-Star Randy Arozarena, the Mariners’ best position player this year. Perhaps a small role could be carved out for him as a DH or replacement for Young at second base against left-handers.

Lazaro Montes, OF

If Seattle’s biggest want is to add power, Montes would be the top choice. The 21-year-old outfielder has slugged 37 homers across stints in Double-A and Triple-A this year, which is second among all minor leaguers. He also leads the Pacific Coast League with nine homers in August.

Swing and miss is a major concern for Montes, though. He has a 30.9% strikeout rate in the minors this year and a 70.5% contact rate when swinging at pitches inside the zone since being promoted to Triple-A on July 7. For reference, Colt Emerson, who ran a 34.4% strikeout rate after being promoted to the majors, had a 27.2% strikeout rate and an 85% contact rate on pitches in the zone while at Triple-A.

There are also some questions about how Montes would fit a roster that is already carrying five outfielders, which includes everyday players like Randy Arozarena, Julio Rodríguez and Dominic Canzone, and trade deadline addition Taylor Ward. However, Ward’s struggles since being acquired potentially leaves the door open for some at-bats at DH and in right field.

Leo Rivas, UTL

Rivas, an unsung hero of Seattle’s 2025 AL West championship team, is batting just .147 with a .460 OPS in 47 MLB games this year. But his positional versatility, baserunning ability and propensity to come up with clutch hits could get him a call back up to the big leagues.

In his most recent stretch in the big leagues, which ended Tuesday when he was optioned to Tacoma, Rivas delivered a walkoff hit and followed it the day after with a two-out RBI base hit in the ninth inning that set up Arozarena’s walkoff home run.

Ryan Bliss, UTL

Bliss has had a solid year while spending most of it in the minors with Tacoma. In 104 games, he’s batting .265 with a .727 OPS, seven homers, 30 doubles, three triples and 24 stolen bases.

Speed and the ability to play both the infield and outfield would be the biggest reasons to promote the 26-year-old Bliss.

Pitchers

Cooper Criswell

Criswell has been out since June 9 with a right shoulder strain, but if he is ready to return by Sept. 1, he seems like the obvious pitching add for a Seattle team that his sorely missed his ability to cover multiple innings in relief.

Criswell began a rehab assignment with Tacoma on Aug. 22, allowing three runs in one-third of an inning in his first game, but he bounced back with a clean inning in his second outing Tuesday.

The right-hander had a 3.52 ERA and 1.17 WHIP with 23 strikeouts to eight walks over 30 2/3 innings before landing on the IL.

Ryan Sloan

While it doesn’t seem all that likely at this point, especially if the M’s believe Matt Brash will return at some point in September in addition to Criswell, there is a chance the Mariners promote touted pitching prospect Sloan to be a member of the bullpen for the final month.

After some initials troubles at the start of this year while making the jump to Double-A at just 20 years old, Sloan has been stellar for the past two months, posting a 2.35 ERA with 57 strikeouts and only three walks over 46 innings in nine starts.

Nick Davila

If Criswell isn’t ready to return by Sept. 1, the M’s could turn to the Davila, a right-hander who has a 4.10 ERA and 1.22 WHIP with 13 strikeouts to 11 walks over 26 1/3 innings in the majors this year.

Josh Simpson

Simpson would be another candidate to join the bullpen if Criswell needs more time. He would give Seattle a third left-handed option in addition to Gabe Speier and José A. Ferrer.

In eight big-league appearances this year, Simpson has a 9.82 ERA and 2.05 WHIP with 10 strikeouts to four walks over 7 1/3 innings.

Seattle Mariners news and more

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