Mariners sign Phillies minor league free agent Gabe Mosser
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Earlier this month, the Seattle Mariners signed 29-year-old right-handed pitcher Gabe Mosser, who had previously pitched for the Philadelphia Phillies organization. The deal was finalized on January 16, but wasn't posted until this week - a common practice for offseason, minor league transactions.
Mosser was originally drafted in the 27th round by the Padres in 2018 and spent six years scuffling in the San Diego system before signing with his hometown Phillies in 2025. In 147 minor league games (101 as a starter), he's compiled a career mark of 30-37 with a 4.62 ERA and 536 strikeouts in 565.1 innings.
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Mosser made 25 starts in 2025, split between Double-A and Triple-A. Mosser posted a 6-9 record with a 5.20 ERA and 127 Ks in 124 2/3 innings. He will be looking to fill a long-reliever and spot-starter role in Spring Training, but he'll have plenty of competition.
Building a better bullpen
The Mariners are set in their rotation and have one of the best closers in baseball in Andres Munoz. They have a potentially lethal left-handed combination in Gabe Speier and Jose Ferrer. But, they have shown some concern for the right side of the bullpen, particularly in middle and long relief.
Having already added pitchers of similar status like Cooper Criswell and Dane Dunning, there's a somewhat undetermined role that the Mariners front office is looking to fill. It could be a full-time spot, or it could be a shuttle back-and-forth to Tacoma, and only being called up when needed. While the early favorite for that spot is likely Dunning, the team has given itself plenty of options with these low-risk signings.
