A U.S. based player from Australia, Gardner played varsity tennis for Southern Methodist University (SMU) while studying for a business degree.

In 1970 Gardner was runner-up at the U.S. National Amateur Grass Court Championships, and was the SWC singles champion in 1972.

[3] In 1971 he won the U.S. National Amateur Grass Court Championships against Raul Ramirez at Southampton, Long Island, New York.

The same year he was a finalist to Dick Dell at the Southern Championships held Birmingham, Alabama On the professional tour he had wins over Georges Goven and Roscoe Tanner.

He beat Nikola Špear in the first round of the 1971 US Open and featured in all grand slam main draws except his home tournament.