"It made a lot of sense in my head," Gaines said. "I'm familiar with the coach and the scheme and the defensive game plan and everything so it was a no brainer for me."
Gaines becomes the second cornerback the team has added this offseason, as the club inked former Houston Texans first-round draft pick Kevin Johnson with a one-year deal earlier in the free agent signing period.
Last season, Gaines played with the Cleveland Browns, starting two games and playing in six before ending the year on injured reserve list with a concussion.
"It's really been frustrating, but that's been my main focus this offseason, making sure I can stay healthy through 16 games this year," Gaines said.
"I really can't change the past and my injury history, but what I can do is make sure I'm ready and prepared for this year."
That season with the Bills he played in 11 games, putting up 59 tackles, nine pass breakups, three forced fumbles and one interception.
Now back with the Bills, Gaines says he's excited to head back to Buffalo to play in a place where he had success just two years ago.
"Like I said, it's great to have those guys still here, who I've already worked with, who I've already won with. It's a good thing."