Williams missed his second straight practice Friday because of a bruised bone and an inflamed ligament in his left ankle. He was hurt when a teammate rolled up on his leg in practice Wednesday.
Coach Chan Gailey says he'll likely wait until game time Sunday to determine whether Williams will play against the Ravens (4-2).
In saying the ankle's feeling better, Williams noted he still felt a twinge when testing it on his own.
In another development Friday, the Bills activated defensive back Jon Corto off the Reserve/Physically Unable to Perform list and waived defensive back Cary Harris. The move came the first week Corto was eligible to return to practice after he had surgery in July to repair a broken left wrist.
Corto is entering his third season and has played a key role on special teams. Harris, a 2009 sixth-round draft pick, saw very limited action in his two years with Buffalo.
The injury to Williams is a significant blow for the Bills (0-5), who are off to their worst start in 25 years, and for a defense that's having enough problems already.
Buffalo's allowed 200 yards rushing in each of its past three games, and a league-worst 912 overall, which is 15 more than Oakland even though the Raiders (2-4) have played one extra game.
"He's a force for us inside. It hurts not to have a player of his caliber on the field," Gailey said, referring to the potential of not having Williams. "But it's an opportunity for somebody else to show what they've got."
Buffalo is coming off its bye, and spent much of the two-week break revamping its defense. After opening the season with a 3-4 formation, the Bills are shifting back to playing four defensive linemen to add more bulk up front in a bid to address their deficiencies against the run.
With or without Williams, rookie second-round draft pick Torell Troup is expected to get more playing time at tackle after enjoying his first career start in a 36-26 loss to Jacksonville on Oct. 10. If Williams can't play, the Bills will likely shift defensive end Marcus Stroud inside to his more natural position to play next to Troup.
Gailey described Troup as a work in progress.
"He is a very talented rookie, but he needs to learn a lot about the game," Gailey said. "And if he has to play a ton this week, he's going to get a baptism by fire."
"I'm very excited to get out there and play," Troup said. "They spent a second-round draft pick on me, and people want to see me perform. And I feel like I can."
Selected 41st overall out of Central Florida, Troup was a three-year starter and a two-time Conference USA selection. Last season, he played a key role in helping the Knights finish fourth in the nation against the run (82.7 yards per game).
Gailey listed reserve linebacker Keith Ellison (knee) as questionable. Gailey ruled out cornerback Terrence McGee (back/nerve problem), who will miss his third straight game, and starting left tackle Cornell Green, who hurt his knee against Jacksonville.
Copyright 2010 by The Associated Press