The 49ers began the day with 15 players on injured reserve. They since have added two more.
Williams may have played his final game for the 49ers as he is scheduled to become a free agent in March.
The 49ers also announced they signed kicker Tristan Vizcaino to the team’s practice squad.
Vizcaino could replace Robbie Gould on Sunday after Gould went on the reserve/COVID-19 list this week.
To fill the other spot on their 53-player roster, the 49ers promoted defensive lineman Alex Barrett from the practice squad. Barrett has played six games and made two tackles.
The 49ers ruled out receiver Brandon Aiyuk (ankle), defensive tackle Kevin Givens (not injury related), linebacker Dre Greenlaw (calf), defensive tackle Javon Kinlaw (knee), receiver Deebo Samuel (hamstring), cornerback Richard Sherman (calf) and cornerback K'Waun Williams (shin).