The Reds designated Mills for assignment Sunday.
Mills will move off both the 40-man roster and 26-man active roster after he was roughed up Saturday in his Reds debut. While working in long relief during the Reds' 12-5 loss to the Padres, Mills recorded three outs and allowed five runs (two earned) on four hits and one walk. The Reds recalled outfielder Stuart Fairchild from Triple-A Louisville to replace Mills on the active roster.