Duckworth left in the fifth inning on Sunday at Texas with a strained elbow. He was 1-5 with a 6.11 ERA in 10 appearances, including eight starts.
Mientkiewicz left last Tuesday's game against Baltimore when he aggravated a sciatic nerve condition in his lower back. He was hitting .283 with four home runs and 43 RBI in 91 games. His placement on the disabled list was retroactive to July 26.
Sanders, who was on the disabled list with a right groin pull and had missed 15 games, hit .244 with nine home runs and 43 RBI in 68 games.
Peralta was recalled from Triple-A Omaha. He was 1-3 with a 4.63 ERA in 38 relief appearances in two previous stints with Kansas City.