Jul 29, 2025; West Sacramento, California, USA; Seattle Mariners pitcher Jackson Kowar (37) throws a pitch against the Athletics during the seventh inning at Sutter Health Park. Mandatory Credit: Dennis Lee-Imagn Images Dennis Lee-Imagn Images

Seattle Mariners designate veteran relief pitcher for assignment

Originally posted on Seattle Mariners on SI
By Ryan Boman | Last updated Jan 28, 2026 9:38 AM ET

The Seattle Mariners have somewhat surprisingly designated reliever Jackson Kowar for assignment on Tuesday. The move was made to clear a spot on the 40-man roster for newly-acquired catcher Jhonny Peredes.

Kowar, 29, was originally acquired by the Mariners as part of the 2023 trade that sent outfielder Jarred Kelenic to the Atlanta Braves. He had moderate success with the M's, but was originally figured in as one of the righthanded arms in the bullpen in 2026.

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Kowar spent last season splitting his playing time between Seattle and Triple-A Tacoma. He made 15 relief appearances with the Mariners last year, posting a 4.24 ERA with 15 strikeouts and seven walks in 17 innings after being activated from the injured list in late May.

Righthanded replacements are ready

Brian Bradshaw Sevald-Imagn Images

While it's not fair to call Kowar 'expendable', his position with the big club became a little shakier with some of the acquisitions the Mariners have made this offseason. Quietly, the team has been stockpiling veteran righthanders that promise to be more effective.

Perhaps the most intriguing name among the new candidates is Dane Dunning, who was once part of the Rangers' starting rotation, making 95 starts and appearing in 122 games overall for Texas from 2021 to 2025. He could be effective in long relief or as a spot starter—doubling his potential value.

Other names include Yosver Zulueta and longshot Gabe Mosser, but for now, Dunning should be viewed as the favorite. In any event, the team will certainly have an upgrade in the role this season