Gaines played collegiately at Loyola Marymount University under Westhead during his senior season of 1987-88 after transferring from UCLA. Gaines averaged 17.4 points per game that season as a teammate of Bo Kimble and Hank Gathers. Gaines also played professionally under Westhead with the NBA’s Denver Nuggets and the Long Beach Jam of the ABA. Gaines served as an assistant coach for Westhead with the Jam and eventually became the head coach in 2005, as well as a Mercury assistant in 2006.

Originally drafted by the Seattle SuperSonics, Gaines spent time with the Nuggets, New Jersey Nets, Philadelphia 76ers and New York Knicks.