On July 31, 2006, Casey was traded to the Detroit Tigers for minor league pitcher Brian Rogers. During the 2006 American League Championship Series against the Oakland Athletics he partially tore his left calf muscle in Game 1. After coming back from his torn calf in Game 2 of the World Series, he became the hottest hitter for the Tigers, belting two home runs and batting .432 in five games. His .432 batting average was one of the best in Tigers postseason history.