Williams, 28, who has been playing in place of injured All-Pro Orlando Pace, suffered a dislocated ankle and a fractured fibula.
"The fibula is an outer bone on the outside of the shin," said head trainer Jim Anderson. "They're going to operate on it (Monday) morning. They're going to put a plate in the fibula, and put a couple screws across the ankle bone."
The 6-7, 320-pound Williams, in his seventh NFL season, was hurt on the second play of the second quarter, and watched the rest of the game on a monitor in the lockerroom.
"The win makes me feel better than anything," Williams said. "Obviously, I would have liked to be out there, but watching in here I saw a different team. I saw passion. It was the best team in the NFL, an undefeated team - and us saying, 'That should be us.'"
Pace, who is recovering from a torn calf, hopes to be ready for next Sunday's contest against the Seattle Seahawks, one of Williams' former teams. He also has played for the New England Patriots.