The San Francisco 49ers are considering what to do at nose tackle now that it is certain Ian Williams is out for the year.As expected, San Francisco coach Jim Harbaugh said Williams is out for the season with a broken ankle he suffered in the team's 29-3 defeat at Seattle on Sunday night. Glenn Dorsey replaced Williams and he will start.Dorsey is a starting-quality player, but the 49ers are thin behind him. San Francisco will surely look to add at the position.