Isaac Mattson brings intriguing fastball to Mariners after 40-man roster shuffle

The Seattle Mariners have claimed 31-year-old right-handed pitcher Isaac Mattson off waivers from the Pittsburgh Pirates. Mattson joins the 40-man roster with one minor league option remaining after posting a 5.35 ERA across 38 appearances for Pittsburgh in 2026. The move comes as Seattle reorganized its roster ahead of the offseason deadline, offering bullpen depth with a unique high-spin fastball profile.

To trim down their roster, the Mariners outrighted five players to Triple-A Tacoma, including veteran slugger Patrick Wisdom, Josh Simpson, Troy Watson, Weston Wilson, and Will Wilson. Wisdom, who hit 35 home runs in Triple-A this season, holds the right to elect free agency rather than accepting the outright assignment.