Marvel Smith, a two-time Super Bowl champion and 2004 Pro Bowl selection, has announced his retirement from the NFL. Smith, who signed with San Francisco in March after nine years with the Steelers, was slowly recovering from offseason back surgery and never posed much of a threat to Niner RT Adam Snyder during the preseason.A second-round pick of the Steelers in the 2000 draft, Smith played in 111 games, starting 108 of them, over his nine-year career. But injuries would hamper the tail end ...