Adrian Peterson unlikely for Week 15

MINNEAPOLIS -- Minnesota Vikings running back Adrian Peterson will not need surgery on his sprained right foot, but is unlikely to play on Sunday against the Philadelphia Eagles, according to a person with knowledge of the situation.

Peterson sustained a mid-foot sprain in the second quarter on Sunday against the Baltimore Ravens, as linebacker Arthur Brown tackled him while he tried to stretch for a first down. X-rays were negative on Peterson's foot, a MRI showed no structural damage or risk of a Lisfranc injury, and Peterson said on Monday afternoon he planned to play Sunday. But he was still scheduled to undergo a CT scan on his foot, and the Vikings planned to send the results of Peterson's medical exams to a foot specialist.

When the Vikings got the results on Monday evening, they determined Peterson would have to spend time in a walking boot and prove he can run once he gets out of the boot, according to the source.

It remains to be seen whether that will happen yet this season. Dallas Cowboys running back DeMarco Murray missed six weeks with a mid-foot sprain last season, and Jacksonville Jaguars running back Maurice Jones-Drew is averaging a career-low 3.5 yards per carry this season after sustaining a Lisfranc injury in 2012 and spraining his foot again this year.

In light of that history, Peterson's typically sunny outlook on his ability to heal quickly might not pan out this time.

"What is often the case is, guys will feel much better [a day or two after a sprain]," ESPN injury analyst Stephania Bell said. "They say, 'This isn't so bad. I can walk around on it.' And then they try and run."

Peterson was leading the NFL in rushing before Sunday's games, and now trails Philadelphia's LeSean McCoy by 84 yards. The reigning NFL MVP has proven to be a quick healer, having returned from ACL surgery in just nine months to run for 2,097 yards last season, but given the Vikings are 3-9-1 and were eliminated from the playoffs with their loss to the Ravens on Sunday, they might not have much reason to rush Peterson back this season.