With Nate Clements out for at least six weeks, the 49ers today signed former Lions cornerback Keith Smith. To make room on the roster, the team released WR Micheal Spurlock. Smith, 29, originally was a third-round pick by the Lions in 2004. He started five games in that span, registering 118 tackles, four interceptions, 14 passes defensed, one sack, one forced fumble and one touchdown.
The 49ers also released tight end Carson Butler from the practice squad.
-- Matt Barrows
