Referring to the injury for the first time as a high ankle sprain, coach Dick Jauron said he's "not particularly optimistic" Lynch will play at Jacksonville on Sunday.
"He wants to play. He still thinks he should've played last week," Jauron said. "But he's just real sore."
Jauron had refused to describe the nature of the injury except to call it more than a normal sprain. Players generally require at least two weeks to recover from a high ankle sprain.
Lynch was spotted briefly in the trainer's room during practice Wednesday. He was wearing street clothes and walking with a noticeable limp.
The first-round draft pick has been out since helping secure a 13-10 win at Miami on Nov. 11. He leads the team with six touchdowns rushing and one passing, giving him a hand in seven of the 11 TDs produced by the Buffalo offense.
Despite missing a game, Lynch still ranks eighth in the NFL with 751 yards rushing, and is tied for third with 196 carries.
Safety Donte Whitner was held out of practice because of a head injury, but Jauron said the team was only being cautious and he expects Whitner to play Sunday.
Whitner was hurt when he tackled Patriots running back Kevin Faulk midway through the second quarter. Whitner continued playing, but Jauron expressed concern when the player had difficulty remembering certain events from the game.
Starting linebacker Angelo Crowell (foot) and cornerback Terrence McGee (Achilles' tendon) practiced on a limited basis.