Vikings running back Adrian Peterson was helped off the field Sunday at Green Bay, walking gingerly on his right leg and favoring his knee. Peterson, a former Oklahoma standout, made an 11-yard catch in the third quarter when he was hit low by cornerback Al Harris in the middle of the field and went tumbling head over heels. The rookie writhed in pain on the field, and players immediately called over trainers.

Peterson spent several minutes on the ground, and then left the field limping with the help of trainers, who appeared to be looking at his knee on the sideline. He also tried to put weight on the leg on the sideline, and later was wearing a sleeve on it.

The team says his return was questionable.

Peterson had the most prolific running day in NFL history last week.