Rookie Jerick McKinnon placed on IR

MINNEAPOLIS -- The rookie season of Minnesota Vikings running back Jerick McKinnon is over due to a low back injury that will require surgery.

The Vikings placed McKinnon on injured reserve on Saturday afternoon, activating defensive end Justin Trattou from the practice squad and signing safety Ahmad Dixon to their practice squad. McKinnon, who first was listed on the injury report with a low back injury on Nov. 13, was inactive for last Sunday's game against Carolina after playing through the injury for two weeks. ESPN NFL Insider Adam Caplan reported McKinnon's surgery will keep him out for eight weeks, but the running back is expected to be ready for the start of the Vikings' offseason workouts.

McKinnon, who initially hurt his back lifting weights at the team facility, finishes his rookie season with 538 yards on 113 carries, and 27 catches for 135 yards. He became the Vikings' featured running back after Adrian Peterson was placed on the commissioner's exempt list while he faced child abuse charges. He still leads the Vikings in rushing yards and yards from scrimmage, and he is third among all rookies in rushing yards.

Without McKinnon, the Vikings will turn to a trio of running backs - Matt Asiata, Joe Banyard and Ben Tate, who all saw carries last Sunday against the Panthers. There's also a chance the Vikings could put Peterson back on the field if he is reinstated from the exempt list by arbitrator Harold Henderson, though it remains to be seen how the team would handle Peterson should he win the appeal of his league suspension.

A third-round pick from Georgia Southern, McKinnon shifted to running back this year after spending most of his college career as a triple-option quarterback. He played in the Senior Bowl as a running back, and impressed teams at the NFL scouting combine with a 4.41-second 40-yard dash, a 40 ½-inch vertical leap and 32 bench-press repetitions at 225 pounds. The Vikings used the third-round pick they acquired from the Seattle Seahawks in last year's Percy Harvin trade to select McKinnon.