Gardner went 20–10 with a 3.51 ERA over two seasons in the Mets' farm system to earn a call up to the majors in September 1965.

He lasted just three innings in his first major league start, giving up seven runs (five earned) in an 8–5 loss to the Houston Astros.

[5] Gardner was traded along with Ron Klimkowski from the Yankees to the Oakland Athletics for Felipe Alou on April 9, 1971.

He spent 1974 in the Detroit Tigers' organization at Triple-A, then in 1975 was back in the Yankees' farm system with the Syracuse Chiefs as pitching coach for manager Bobby Cox and even appeared in 10 games before announcing his retirement as an active player.

[10] He died in Binghamton, New York, on October 21, 2023, at the age of 78, and was survived by his two children, three grandchildren, sister, niece and great nephew.