Cooper Criswell: Everything you need to know

Criswell earned the save in Sunday's 8-0 win over the Guardians, allowing two hits while striking out five over three scoreless innings. Criswell was sharp Sunday, limiting the Guardians to a pair of singles to close out Seattle's shutout victory, earning his second career save. The 29-year-old Criswell made the team as a long-relief option after posting a 2.51 ERA across 14.1 innings in spring training. While he may have a defined role in the Mariners' bullpen, don't expect Criswell to be a frequent source of saves. The right-hander has a career ERA of 4.42 with a 1.42 WHIP across 158.2 major-league innings.

Criswell is competing for the final starting spot in Seattle's Opening Day rotation, per Daniel Kramer of MLB.com. With Bryce Miller (oblique) unlikely to be available by the start of the regular season, the Mariners' fifth rotation spot will likely come down to Criswell or Emerson Hancock. While Hancock is the early favorite for the job, the 29-year-old Criswell has added his name to the mix thanks to a strong spring. He's allowed just two runs on seven hits across 10.1 innings while striking out 10. Criswell spent most of the 2025 season in Triple-A, where he posted a 3.70 ERA across 65.2 innings. He did make 18 starts for the Red Sox in 2024, working to a 4.08 ERA with a 1.35 WHIP and 73 strikeouts across 99.1 innings. If Criswell doesn't crack the Opening Day rotation, he'll likely start the year as the long man in Seattle's bullpen.

The Mets traded Criswell to the Mariners on Friday in exchange for cash, Jorge Castillo of ESPN.com reports. The 29-year-old was DFA'd by the Mets on Wednesday following the team's acquisition of Freddy Peralta and Tobias Myers, but Criswell will recapture a 40-man spot upon moving to Seattle. He posted a 3.57 ERA and 1.58 WHIP in 17.2 regular-season innings with the Red Sox in 2025 and will compete for a spot in the Mariners' bullpen during spring training.