Dorsey's absence left the 49ers without a proven option at nose tackle, which was evident in the team's preseason opener when it allowed 237 rushing yards in a 20-point loss to the Ravens.
But the team got some welcomed news Tuesday when fourth-year nose tackle Ian Williams was activated off the physically unable to perform list after breaking his ankle in Week 2 last season.
Williams fractured his left fibula and suffered ligament damage to his ankle when Seahawks guard J.R. Sweezy chop-blocked him at the line scrimmage during a running play. In March the NFL ruled that such blocks will be illegal going forward. Lineman must cut-block in front of a player for it to be legal. Blocks from the side and the back will be flagged for "clipping."
Legal or not, the play had profound impact on Williams' career. His broken ankle required four surgeries. The most recent came in February to remove a plate holding the ankle in place.
Williams entered 2013 as the starting nose tackle before his injury allowed for Dorsey to take over in base situations, where he flourished. Still, nose tackle is a position that gets roughly 15 snaps a game, or even less against teams that run three or more receiver sets regularly. The 49ers take the nose off the field in favor of a cornerback in those situations.
Williams, 24, has appeared in just six games since going undrafted out of Notre Dame in 2011. Former practice squad player Mike Purcell was working at nose tackle with the first team after Dorsey went down.
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