Graterol will be called up to the majors after rosters expand Sept. 1, the Minneapolis Star Tribune reports.
He'll join the Twins after the completion of Triple-A Rochester's regular season Tuesday. Graterol dominated at the Double-A level this season with a 1.78 ERA and a 49:21 K:BB in 50.2 innings. He then was moved to the bullpen and promoted to Triple-A (5.06 ERA and seven strikeouts in 5.1 innings). With a fastball that hits triple digits on the radar gun, he could be an impact reliever in September.