Williams sustained the injury in the first quarter, when Seahawks’ guard J.R. Sweezy’s helmet hit Williams on his left knee on a block. Williams was able to walk off the field with assistance from the 49ers’ medical staff, but obviously the injury seems more serious than it looked.
Williams signed a two-year extension worth $3.5 million in the offseason after playing sparingly last season. He went undrafted out of Notre Dame in 2011.
His injury means that Glenn Dorsey, who was signed in the offseason in free agency, will take over the starting job.
Dorsey, the fifth overall pick in the 2008 draft by the Kansas City Chiefs, played in just four games last season and recorded seven tackles. His best season came in 2010, when he started all 16 games and had 69 tackles and two sacks.
Dorsey was a highly-touted prospect in college, winning the SEC Defensive Player of the Year award in 2007, but has never quite lived up to his expectations in the NFL.
Perhaps a change of scenery and playing time on a Super Bowl-contending team will benefit him.