Peterson said his ankle "got rolled up" when he was tackled on a 1-yard carry late in the second quarter. Neither Peterson nor interim coach Leslie Frazier would speculate on the running back's prospects for next week's game against Buffalo.
"We'll know a little more about Adrian tomorrow," Frazier said, "after they do whatever examinations they have to."
A source told ESPN's Ed Werder that Peterson is expected to undergo an MRI on Monday to determined the damage in his ankle.
The Vikings initially said Peterson was probable to return to the game, then downgraded him to questionable. He had his ankle taped, then stood on the sideline testing it, stepping gingerly at times and attempting short sprints.
"It started to throb a little bit," Peterson said. "I was trying to keep it loose, jogging, but it really didn't help out."
Peterson went over the 1,000-yard mark for the fourth time in his four-year NFL career before he was hurt. He finished with six carries for 36 yards, including a 5-run touchdown run on Minnesota's opening drive.
With Peterson out, rookie Toby Gerhart carried the load, rushing for 76 yards on 22 carries. The second-round draft pick had only 86 yards for the season entering the game.
"Toby Gerhart, man, take my hat off to him and our offensive line, just understanding our situation," Frazier said. "We came in at halftime, we had an idea that Adrian might not be able to go in the second half, and we wanted to emphasize that it wouldn't change our game plan. We were going to trust our offensive line to do what we talked about all week long, and they didn't flinch."
Vikings defensive lineman Ray Edwards left the game in the first half with a left leg injury. He will also get an MRI on Monday, the source told Werder.
Guard Steve Hutchinson injured his left thumb so severely it was taped after the game and a member of the equipment staff had to tie the player's shoes after the game.
Redskins cornerback Carlos Rogers injured his left hamstring in the second half. An injury to Rogers' right hamstring kept him out of the previous week's win over Tennessee.
Information from The Associated Press contributed to this report.