The Rays informed Kolarek on Tuesday that he made the Opening Day roster, Josh Tolentino of The Athletic reports.
Tampa Bay chose to keep Kolarek over Emilio Pagan as its last reliever, with manager Kevin Cash citing Kolarek's status a southpaw as the main factor in the decision. Kolarek, who made 31 appearances for the big club a season ago, will likely see the overwhelming share of his opportunities versus lefty-heavy lineups. He has held opposing lefties to a .234/.279/.313 slash line over parts of two seasons in the big leagues.