Williams (ankle) sat out San Francisco's practice Wednesday, Josh Dubow of The Associated Press reports.
Williams suffered an ankle injury in the team's Week 6 loss to the Browns and hasn't played since. The 35-year-old originally looked to return to practice this week and will still have a chance to do so either Thursday or Friday, but if he ends up being unable to play versus Jacksonville on Sunday, Jaylon Moore will start at left tackle again.