Mariners Claim Isaac Mattson Off Waivers From Pirates

• The Mariners have claimed relief pitcher Isaac Mattson off waivers from the Pirates.
• Mattson had a 2.45 ERA in 44 relief appearances for the Pirates in 2025.
• He struck out 45 batters in 47.2 innings and held opponents to a.203 batting average.
• The Pirates placed Mattson on outright waivers, allowing the Mariners to claim him.
• The Mariners' 40-man roster is now four players over capacity, requiring roster adjustments.