The move was made before Friday's game against Tampa Bay. Santana was in the lineup, batting leadoff.
Utility man Chris Herrmann was optioned to Triple-A Rochester to make room on the roster for Santana, who missed 17 games because of a bone bruise in his left knee. Santana, who came up as a shortstop but was moved to center, where the Twins have been short-handed, played three games on a rehabilitation assignment at Class A Fort Myers.
Before the All-Star break, Santana batted .328 with two home runs and 16 RBIs in 37 games.