The Seattle Mariners have bolstered their pitching depth by acquiring right-handed pitcher Cooper Criswell from the New York Mets in exchange for cash considerations. Criswell was designated for assignment by the Mets after New York acquired Freddy Peralta and Tobias Myers from the Brewers. In response, the Mariners designated left-hander Jhonathan Díaz for assignment to make room on the roster. Reports from Jorge Castillo of ESPN first confirmed the acquisition, while Ryan Divish of The Seattle Times noted the cash transaction.
Criswell Brings Big-League Experience And Versatility Despite Roster Challenges Ahead
Criswell, 29, is viewed as a versatile swingman capable of starting or pitching out of the bullpen. His most extensive big-league experience came with the Boston Red Sox in 2024, when he made 18 starts and eight relief appearances, totaling 99 1/3 innings. That season, he posted a 4.08 ERA with a 17.2% strikeout rate, a 7.2% walk rate, and induced ground balls on 50.3% of balls in play.
Cooper Criswell (MLB)Despite these solid numbers, Criswell’s role diminished in 2025 as Boston strengthened its rotation with Garrett Crochet, Walker Buehler, and Lucas Giolito’s return from injury. Criswell made only seven major league appearances that year and spent most of the season in Triple-A, throwing 65 2/3 innings with a 3.70 ERA, 24.5% strikeout rate, 10.1% walk rate, and 49.4% ground ball rate.
Criswell had exhausted his final minor league option in 2025, leaving him in a precarious roster position. In November, he and the Red Sox agreed on a $800,000 contract for 2026, slightly above the league minimum, designed to discourage other teams from claiming him via waivers. However, the plan did not work as intended, as the Red Sox designated him for assignment in December and the Mets claimed him. The Mets then removed him from their roster, allowing Seattle to act and secure him.
Criswell Adds Versatile Pitching Depth While Mariners Adjust Rotation And Bullpen
Seattle already boasts a strong starting rotation featuring Logan Gilbert, George Kirby, Bryan Woo, Bryce Miller, and Luis Castillo. Beyond the top five, depth is limited, with pitchers like Logan Evans, Emerson Hancock, and Blas Castano yet to establish themselves as reliable major leaguers. Prospect Jurrangelo Cijntje is on the way but only has seven Double-A starts, making Criswell a useful insurance option.
Criswell could serve as a long reliever if necessary, but Seattle’s bullpen is already crowded. The projected eight-man relief corps includes Andrés Muñoz, Matt Brash, Jose A. Ferrer, Eduard Bazardo, Gabe Speier, Carlos Vargas, Casey Legumina, and Jackson Kowar. Most cannot be optioned to the minors, leaving limited roster flexibility. The Mariners may explore passing Criswell through waivers or making other roster adjustments to create space.
Díaz, 29, had been part of Seattle’s rotation depth alongside Evans, Hancock, and Castano, but the Mariners appear to prefer Criswell in that role. Díaz has a brief major league track record, with 46 1/3 innings across five seasons. He posted a 4.66 ERA, 15.1% strikeout rate, 12.3% walk rate, and 45.2% ground ball rate. Most of 2025 was spent in Triple-A Tacoma, where he threw 138 2/3 innings with a 4.15 ERA, 19.8% strikeout rate, 4.1% walk rate, and 46.9% ground ball rate.
Díaz will remain in DFA limbo for a maximum of one week. The waiver process lasts 48 hours, giving the Mariners time to field trade interest. If Díaz clears waivers, he could elect free agency due to a prior career outright, giving him some control over his next move.
The Mariners’ acquisition of Criswell strengthens their pitching depth as the team prepares for the 2026 season. While the rotation and bullpen are already competitive, adding a versatile right-hander provides insurance against injuries or performance fluctuations. Meanwhile, Díaz’s designation reflects the organization’s prioritization of immediate pitching depth over long-term potential. Seattle now has more flexibility to navigate the challenges of a long season, with Criswell potentially serving as a key swingman or bullpen option.
