Padilla was optioned to Triple-A Iowa on Wednesday, Meghan Montemurro of the Chicago Tribune reports.
Padilla served as the 27th man for Tuesday's doubleheader against the Cardinals and allowed a run over 1.2 frames in his big-league debut. The 25-year-old will now return to Iowa, where he has a 1.69 ERA, 1.18 WHIP and 14:6 K:BB since being promoted from Double-A in late July.