He played professionally for three games for the Kentucky Colonels during the 1967–68 American Basketball Association season after a four-year stint with the Harlem Globetrotters.
Gaines attended LeMoyne-Owen College from 1959 to 1963 where he was the first player to have his number retired.
He replaced Dick Vitale at the former school, and coached Michael Cage and future Baseball Hall-of-Famer Tony Gwynn at the latter.
He compiled a 112–117 record in eight seasons at San Diego State University (SDSU) and became the first black head coach in NCAA Division I in California.
He was named the coach of the year of the Western Athletic Conference in 1984–85, when the Aztecs went 24–8 and qualified for the NCAA tournament.