Williams (hamstring) is inactive for Saturday night's game against the Seahawks, Briana Jeannel of the 49ers' official site reports.
Williams played just one snap in the 49ers' Week 17 win over the Bears, and his absence for Saturday night's matchup is a huge blow for a 49ers squad that is attempting to acquire the NFC's top seed. Austen Pleasants is set to start at left tackle in Williams' absence.