Mills was 1-0 with a 6.00 ERA in three exhibition games with the Angels. In his only major league appearance last season, Mills threw five scoreless innings and allowed three hits on July 8 against Baltimore and gained the victory. He was 5-10 with a 5.86 ERA in 19 starts and two relief appearances at Triple-A Salt Lake.
He is 3-3 with a 7.76 ERA in 15 career big league games.
Right-hander Neftali Feliz, who had reconstructive elbow surgery last August, was put on the 60-day disabled list to clear a roster spot.