Ontiveros had 8 saves with a 1.93 ERA as a rookie in 1985 and saved 10 while leading the A’s with 46 appearances in 1986. He became a starter in 1987, then was released after injuries limited him to only 10 starts (3-4, 4.61) in 1988. He signed with the Phillies for 1989 but spent most of the season on the DL.