Peterson had an MRI on his left ankle that revealed a Grade-1 sprain, the least severe of the classifications. X-rays done at the Metrodome on Sunday revealed no fracture or break.
Frazier said Peterson was wearing a walking boot that would be on for the next several days, but the team could attempt to test his condition on Friday. However, Frazier said they won't push him to return to action until he is ready.
"We don't want to put him at risk. You know how valuable he is to our team and our franchise," Frazier said. "So we'll monitor where he is and try to make a good decision with what's best for him and what's best for our team as well."
"… We'll try to see if he's able to do anything on Friday to determine if he'll be able to play on Sunday or not, so we'll get a better feel at that point where he is," Frazier said. "The good news is there's nothing more serious than that, the fact that it is an ankle sprain and he'll recover from it."
Peterson suffered the injury on a 12-yard run in the first quarter when Raiders safety Michael Huff tackled Peterson and the running back's foot bent awkwardly. He was assisted off the field, checked on the sidelines by doctors and trainers and then carted off the field to get X-rays after rushing six times for 26 yards and a touchdown.
He returned to the sidelines in the second half with his pads still on, putting weight on the foot, but eventually he took the pads off and was relegated to an observer.
Frazier said the Vikings' 2-8 record won't factor into when Peterson returns to action.
"You've got to make sure that he's able to protect himself if you get him back on the field. You don't want to put him at risk for obvious reasons, so we'll be measurable about how we go about it," Frazier said. "We want to be cautious. But at the same time you want to be aggressive, but not to the point where he's at risk. So we'll try to be wise as we're evaluating his progress."
Peterson missed the Vikings' Dec. 20 game last year against the Chicago Bears with ankle and knee injuries. Before that, the last time he missed injuries was in his rookie season when he suffered a knee injury against the Green Bay Packers.
This year, he has 872 yards rushing and 11 touchdowns in 10 games played.
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.