The Rockies made the move Tuesday, retroactive to Monday.
Podsednik was hitting .263 with one home run and 15 RBIs in 75 games for the Rockies with 10 stolen bases. He was 3-for-5 with two steals Sunday against Cincinnati.
Sullivan is batting .306 with six home runs and 40 RBIs in 83 games for Triple-A Colorado Springs. He was part of the Rockies' roster for the World Series last season.
Arias pitched in 12 games for the Rockies this season, going 0-0 with a 2.63 ERA.