Poppen signed a minor-league contract with the Mariners on Jan. 18 and received an invitation to major-league spring training.
Poppen spent all of last season with the Padres' Triple-A affiliate, accumulating a 6.33 ERA and 1.88 WHIP across 58.1 innings in 47 appearances. Barring a significant turnaround from the 29-year-old righty during spring camp, Poppen should return to Triple-A to begin the new season.