SEATTLE – Seattle Mariners Executive Vice President & General Manager of Baseball Operations Justin Hollander announced today that the Mariners have claimed RHP Isaac Mattson off waivers from the Pittsburgh Pirates.
The Mariners 40-man roster is now at 36 players.
Mattson, 31, appeared in 38 games with the Pirates in 2026, posting a 5.35 ERA (23 ER, 38.2 IP), 18 walks, 36 strikeouts and a 1.60 WHIP.
Mattson has appeared in parts of 4 Major League seasons with the Orioles (2021) and Pirates (2024-26), going 3-3 with a 3.94 ERA (42 ER, 96.0 IP), 47 walks, 90 strikeouts and a 1.38 WHIP in 89 career games.
The 6-foot-2 right hander was originally selected by the Los Angeles Angels in the 19th round of the 2017 MLB First-Year Player Draft out of the University of Pittsburgh (PA). He has appeared in parts of 9 minor league seasons in the Angels (2017-19), Orioles (2021-22), Twins (2023) and Pirates (2024-26) organizations, going 30-12 with a 3.23 ERA (136 ER, 378.2), 172 walks and 460 strikeouts in 211 games (16 starts).
