Washington Redskins running back Adrian Peterson has a grade 1 high ankle sprain and a grade 2 low ankle sprain, he told ESPN's Josina Anderson on Tuesday.

Despite those injuries, Peterson said "I'm good" for Thursday night's game against the Minnesota Vikings, his former team.

Peterson, 34, had a MRI on Monday. He suffered the injury in Sunday's 9-0 loss to the San Francisco 49ers. He rushed 20 times for 81 yards and fumbled once.

Wendell Smallwood had five carries for 23 yards Washington.

The Redskins on Sunday were without running back Chris Thompson, who has a toe injury.