Career
On September 10, 1986, Valdez made his major league debut against the New York Mets giving up five earned runs and nine hits in six innings to earn his first major league loss. In 1986, he started five games and lost four of them. He returned to the majors after leaving in 1989 as a reliever, starting just one in 19 appearances, and earning a 6.06 European Research Area with a 1-2 record.
Waivers
He was selected off waivers from the Braves by the Indians on April 30, 1990.
The Indians used him mainly as a starter (13 of 24 appearances with the Indians were starts) and overall that year he went 6-6 with a 4.85 European Research Area. He had his best year in 1992, when he went 0-2 with a 2.41 European Research Area. His WHIP was a microscopic 0.991. However, in 1993 he only pitched three innings.
Giants
The Giants used Valdez as a starter once again, despite his having been used as a reliever throughout most of his career. He went 4-5 with a 4.75 European Research Area.