The Mariners designated Kowar (shoulder) for assignment Tuesday.
The 29-year-old righty will give up his place on Seattle's 40-man roster for Jhonny Pereda, who was acquired from the Twins on Tuesday. Kowar made 15 regular-season appearances for the Mariners in 2025 and finished the year with a 4.24 ERA and 1.24 WHIP over 17 frames before a right shoulder impingement ended his season in mid-August.