 He was drafted again in 1975 by the San Francisco Giants, but did not sign, instead waiting until the following January, when he was drafted in the secondary phase by the Padres.Shirley skipped several levels of minor league baseball, being assigned directly to the Double-A Amarillo Gold Sox to start the 1976 season.After posting a win–loss record of 9–5 with a 3.32 ERA in 16 starts, he was promoted to the Triple-A Hawaii Islanders, finishing the season there.