Manuel threw for 1,972 yards and 11 touchdowns in 10 appearances as a rookie last season, but a troublesome knee ended his campaign early and he required three separate operations to fix it.
With his surgery behind him, Manuel is now eager to get back on the practice field and lead the Bills to the playoffs for the first time since 1999.
He told reporters: "I definitely agree there's a lot out there for myself as a quarterback to get better. Last season, I had some success and I had some bad games as well. It's obvious.
"My knee feels fine. I feel normal. I'm very eager to play a full 16-game regular season and see how I can perform."
Manuel will once more be competing for the starting job with Thad Lewis, who stepped into his position following his injury last term.