Another star member of San Francisco's vaunted defense is calling it a career. The 49ers announced late Monday that linebacker Chris Borland is retiring after one season, without offering specifics. Borland told ESPN's ''Outside the Lines'' earlier Monday that he is retiring following his standout rookie season because of concerns about head trauma. ''While unexpected, we certainly respect Chris' decision,'' 49ers general manager Trent Baalke said. More...