We reported earlier that 49ers cornerback Chris Culliver was undergoing an MRI on his knee.
According to Ian Rapoport of the NFL Network, Culliver suffered a torn ACL.
I'm told #49ers CB Chris Culliver tore his ACL today during practice. Terrible. A late MRI revealed the news.
— Ian Rapoport (@RapSheet) August 2, 2013
This is a big blow to the 49ers secondary.