The right-hander missed the minimum amount of time after being placed on the DL on July 6 with right shoulder tendinitis. The team was targeting Tuesday's game for Garza's return.
Garza missed just one turn through the rotation because of the All-Star break. He last pitched on July 2, giving up four runs and 10 hits in six innings in an 8-7 win at Philadelphia.
Garza is 4-10 with a 5.55 ERA in 17 games on the season.
Milwaukee optioned right-hander Tyler Cravy to Triple-A Colorado Springs on Monday to make room for Garza.