The results of Williams' MRI have not been revealed.
Over four games this season, Williams has recorded eight tackles and one sack and helped the Bills rank second in the league in fewest rushing yards allowed per attempt (2.9).
The 31-year-old has played in all 16 games the past two seasons.
"I just heard that we're going to see how it progresses. He's been around, he's walking around here," coach Doug Marrone said. "That's the doctors. When they release him, they release him, and when they don't ... I don't have a feel. All I know is how it progresses, I'll know more as the week goes."
Williams, the Bills' longest-tenured player and a defensive captain, might not have to practice in order to play.
"I think Kyle is one of those players that doesn't have to practice and can go in there and play," Marrone said. "There's not many players like that."