49ers activate NT Ian Williams

The San Francisco 49ers received much-needed reinforcement on the defensive line with the activation of nose tackle Ian Williams from the physically unable to perform list Tuesday.

Williams was the starting nose tackle last year but broke his leg at Seattle in Week 2 and was lost for the season. He required four surgeries, the last coming in February. Barring a setback, it is not out of the question that Williams will be ready to play Week 1 of the regular season at Dallas on Sept. 7.

Glenn Dorsey, who ably replaced Williams last season, suffered a torn biceps Aug. 1. He could be out for the entire season.

The 49ers have several other players dealing with varying degrees of injuries on the defensive line. They finished their first preseason game, at Baltimore on Thursday, with four healthy defensive linemen.