The San Francisco 49ers have retained nose tackle Ian Williams on a new deal before free asgency. It's a five-year contract. Williams has emerged as an important performer in the middle of the 49ers' defense, which lost linebacker Patrick Willis to retirement last March followed by Chris Borland and veteran defensive end Justin Smith. Aldon Smith also was released, then joined the Oakland Raiders before being hit with a yearlong suspension. Williams had 65 tackles, a sack and a forced fumble last year during a 5-11 season. Follow me on Twitter: @AaronWilson_NFL Aaron Wilson covers the Texans for the Houston Chronicle.