Thomas Clayton tears ACL

Although one of the running backs who sprained a knee during Friday night’s Broncos-49ers preseason tilt in San Fran emerged with good news, the other one wasn’t so lucky.

Niners tailback Thomas Clayton has a torn ACL, according to a league source.

Clayton was a sixth-round pick in 2007.  He spent his rookie year and most of 2008 on the practice squad.  He was elevated to the active roster for the last two games of the 2008 season.