Wochit News - San Francisco 49ers defensive lineman Justin Smith is retiring.Smith announced his decision on Monday in the latest blow to the 49ers this offseason.Two other defensive stars have also retired in linebackers Patrick Willis and Chris Borland.Smith played 14 seasons in the NFL after being drafted in the first round by Cincinnati in 2001.After seven seasons with the Bengals, he signed as a free agent in San Francisco and had his best success in seven years with the 49ers.