Legumino will serve as the Mariners' opening pitcher in Tuesday's game against the White Sox, Shannon Drayer of SeattleSports.com reports.
He'll likely go an inning or two before handing things off to bulk reliever Casey Lawrence. Legumina has managed a 1.84 ERA in 15 relief appearances for the Mariners this season, although that has come with eight walks over 14.2 innings.