Minneapolis, MN (SportsNetwork.com) - The Minnesota Vikings formally ruled starting quarterback Christian Ponder out for Sunday's game at Baltimore after failing to receive medical clearance for a concussion he sustained last week.
Star running back Adrian Peterson, meanwhile, is listed as questionable to face the Ravens due to a groin injury. The reigning NFL MVP did put in a limited practice on Friday, however, after sitting out the previous two days to receive treatment.
Ponder was knocked out of last Sunday's matchup against Chicago after taking a shot to the head in the first half. Matt Cassel took over under center and rallied Minnesota to a 23-20 overtime win.
Cassel, who went 20-of-33 for 243 yards with one touchdown and one interception in relief, had been named the Vikings' starter for Sunday's tilt by head coach Leslie Frazier on Wednesday.
Tight end Kyle Rudolph and cornerback Josh Robinson also will not play against the Ravens. Rudolph has been sidelined since Week 9 with a broken foot, while Robinson has missed the club's past two outings with a fractured sternum.
Safety Jamarca Sanford (ankle) was declared questionable as well for the Baltimore game, but was able to practice in full on Friday.