Peterson injured his right ankle with 10 minutes left in the first half Sunday when Redskins linebacker Lorenzo Alexander landed on it while making a tackle.
Peterson, who eclipsed the 1,000-yard rushing mark for the season and scored his 50th career touchdown before the injury, was scheduled have a magnetic resonance imaging test on his ankle Monday, but interim head coach Leslie Frazier said at his day-after press conference that they haven't gotten the results of that.
"We are still going through the process and just trying to determine the severity of it," Frazier said. "We'll probably learn a little bit more, probably on Wednesday when we come back and just see what he can or can't do."
After rushing for 36 yards on six carries, Peterson wanted to try to return to the game and had his ankle taped twice, but trainers told him and Frazier that he would be best served sitting out the rest of the game.
"We had a little bit of that yesterday. He wanted to get back in the game. He's coming up to me – of course, I don't know, I'm keeping up with what's happening on the field and what's going on there," Frazier said. "I just got our trainer to fill me in on where he was. They just said, ‘Nope, let's hold him.' That's what I'll do again – I'll defer to our trainers. They'll tell me when he's ready to go."
In more than three-and-a-half seasons in the NFL, Peterson has missed only two games. Those both came in 2007 after a knee injury suffered against the Green Bay Packers, one week after setting the NFL single-game rushing record with 296 yards against the San Diego Chargers, but he hasn't missed a full game since.
With Peterson down, rookie Toby Gerhart stepped and carried 22 times for 76 yards, easily the most opportunities and production he has had in his 11-game career. Gerhart left the game for a short time in the third quarter with what Frazier said was a shoulder stinger, but he returned on the next series.
With Albert Young inactive against the Redskins, the Vikings would have turned to fullback Naufahu Tahi as their main running back. Frazier said versatile offensive weapon Percy Harvin might not hold up to the pounding that every-down running backs take if he were lined up in the backfield on a regular basis.
"I think it will always just be sprinkled in. I don't know if he has the body to continuously take handoffs," Frazier said. "He's been a very good wide receiver for us. It will probably be more like what you see now."
The Vikings worked out running back Lorenzo Booker last week, but Frazier said they would likely wait and see how severe Peterson's injury is before making a signing at the position.
Peterson wasn't the only player hurt during Sunday's game. Defensive end Ray Edwards also sprained his ankle. Frazier said Edwards' sprain was similar to Peterson's, but Edwards tweeted on Monday morning that he received good news on his injury.
In addition to the ankle sprains, Pro Bowl guard Steve Hutchinson sprained his thumb. Hutchinson didn't leave the game.
"I just saw him a moment ago," Frazier said. "I just shook my head, because I know he was in pain, but he continued to play, and for an offensive lineman who's using his hands all the time, that's not an easy task."
The Vikings entered the game with cornerback Chris Cook and wide receiver Bernard Berrian on the inactive list. Frazier said the decision with Cook was injury-related, not because the rookie had struggled in recent weeks.
"That knee was acting up a little bit. On Friday, he really wasn't pushing off the way we needed him to," said Frazier. "Just thought it wouldn't be wise to try to get him on the field and go out and perform. We were counting on him up until that point."
Cook had arthroscopic procedures on both of his knees after suffering separate meniscus tears in late August and September.
"He's had swelling in both knees so that's a concern," Frazier said.
Cook had started at right cornerback the last two games, but Asher Allen made his seventh start of the season with Cook out of action.
"Asher Allen did a great job. In general our entire secondary played well, I thought yesterday," Frazier said. "(The Redskins) had the one explosive play, but you include the way our defensive line played, our linebackers, but our entire defense just had a heck of a football game all the way around."
Tim Yotter is the publisher of Viking Update. Follow Viking Update on Twitter and discuss this topic on our message boards. To become a subscriber to the Viking Update web site or magazine, click here.