Coach Mike McCarthy says that plans are to either move outside linebackers A.J. Hawk or Brandon Chillar to the middle, or to have Desmond Bishop step up in place of Barnett.
Barnett was injured on the Vikings' first drive of the second half while trying to tackle Peterson.
Barnett, a first-round draft pick in 2003, was named a Pro Bowl alternate last season after receiving a contract extension through 2012.
This certainly doesn't help the Packers' at all. First, defensive end/tackle Cullen Jenkins goes down, and now Barnett. Both players are key to our defense, and with their absence, it certainly will make it a tough ride the rest of the way.