Buffalo also signed cornerback Levi Wallace from the practice squad in a corresponding transaction. The Bills announced the moves on Tuesday.
Gaines was the team's No. 2 cornerback this season behind Tre'Davious White, but struggled with penalties. He has been assessed the most penalty yards in the league in seven games this season, while making 30 tackles and defending two passes.
Gaines returned to the Bills' starting lineup after suffering an injury in Week 6 against the Houston Texans. He joined the Bills this spring as a free agent. Gaines initially entered the league as a third-round pick by the Kansas City Chiefs in the 2014 NFL Draft. He played his first four seasons for the Chiefs, amassing 99 tackles, 14 passes defensed, two forced fumbles and an interception in 41 games.
For his career, Gaines has 129 tackles, 16 passes defensed, two forced fumbles and an interception in 48 games. He has 22 career starts.
Wallace was a walk-on at the University of Alabama. He was originally signed by the Bills as an undrafted free agent, but was released before the start of the regular season and joined the practice squad.
The Bills face the New York Jets at 1 p.m. on Sunday at MetLife Stadium in East Rutherford, N.J.