The team made the announcement Monday morning, saying that his playing status will now be determined by head coach Doug Marrone and staff.
Manuel practiced for the first time on Wednesday, but did not play Sunday. He has not played since early October after a sprained knee ligament.
Manuel's return gives the Bills some good news at quarterback after a tumultuous preseason at the position.
Veteran Kevin Kolb, who was competing with Manuel for the starting quarterback job, was placed on injured reserve on Aug. 30. Kolb suffered a concussion against the Washington Redskins on Aug. 24. Kolb also missed time at training camp because of a left knee injury after tripping on a wet rubber mat between practice fields.
With Kolb and Manuel injured, the Bills briefly had only one healthy quarterback in undrafted rookie Jeff Tuel. Buffalo added Thad Lewis as a member of the practice squad, but he has been out with sore ribs.