Gaines was one of only 13 African American students to volunteer to integrate Elbert County High School in Elberton, Georgia [citation needed].
In the 1976 season, he led all NFL rookies with 724 yards rushing despite not starting until the seventh game, set a franchise record with four 100-yard rushing games in a single season, and was selected AFC Offensive Rookie of the Year by NFL Players Association.
The Sporting News named him the best running back in the AFC East and the most individual offensive improvement in the division in 1979.
He "wore many hats" for the Jets: although technically a running back, he was also a prolific receiver, was an intimidating blocker in short yardage situations, and played special teams.
Gaines has been employed with the NFL Players Association for 22 years, and in April 2008 was promoted to Assistant Executive Director.