EDEN PRAIRIE, Minn. -- After seeing Adrian Peterson work out on Friday, the Minnesota Vikings listed him as questionable for Sunday's game against the Philadelphia Eagles. But the fact that Peterson even got to this point seemed to amaze coach Leslie Frazier -- and Peterson himself.

Frazier said earlier in the week that he was more optimistic about running back Toby Gerhart playing with a strained hamstring than he was about Peterson getting on the field a week after spraining his right foot. A source with knowledge of the situation also told ESPN.com on Monday that it was unlikely Peterson would play Sunday, though the source added the Vikings would know more after Peterson tried to run and work out.

Multiple exams showed Peterson would not need surgery on his foot, the source said this week, so Friday's workout was going to be a matter of whether Peterson could show enough speed and explosiveness to get the Vikings to think about playing him on Sunday. While they won't make a final decision until Saturday or Sunday, Frazier said, they were certainly more optimistic on Friday than they were earlier in the week.

"He was able to plant. He was able to push off," Frazier said. "We'll see tomorrow if there's any soreness, but he looked far better than I anticipated."

Peterson vowed several times this week -- to reporters on Monday, and to Frazier on Wednesday -- that he would be ready to play on Sunday. He'd already proved how quick of a healer he was when he ran for 2,097 yards less than a year after ACL surgery in 2012, and Peterson might have a chance to show that again this week.