Why hasn't Adrian Peterson been declared out for Sunday? It's Brett Favre's fault

And here you thought the Vikings had vanquished the ghost of Brett Favre? Nope. Not totally.

Favre made his presence felt around Winter Park again Friday afternoon. Not literally of course. The Ol' Gunslinger is off dabbling in retirement somewhere. But when the Vikings filed their official injury report for Sunday's game in Atlanta, Favre had a small peripheral influence. You see, star running back Adrian Peterson is listed as doubtful for the contest at the Georgia Dome. Peterson suffered a high ankle sprain last Sunday in a home loss to Oakland. He was in a walking boot earlier in the week and didn't practice Wednesday or Thursday. And on Friday, Peterson, while now out of the boot, was moving around gingerly as he did some minor testing of the ankle on the side.

To make a long story short, the chances of Peterson playing against the Falcons are slimmer than the chances of the Vikings making the playoffs. The risk-reward scenario leaves only one logical choice: sit A.P.

But Vikings coach Leslie Frazier knew better than to stamp a definitive "out" tag on Peterson on Friday. Why? Because last December, at the tail end of Week 15, Frazier declared Favre out for the Vikings' Monday night game with Chicago. The veteran quarterback was dealing with agonizing pain in his sternoclavicular joint and a nerve issue near his neck that was causing numbness in his hand. Then, somehow, the following Monday afternoon, Favre had recovered enough to give things a try. And Frazier and the Vikings were forced to file an amended injury report with the NFL, upgrading Favre from out to questionable.

Favre started that night against the Bears and Frazier learned something new about declaring a player out.

"Hey," Frazier said Friday, "you've got to be very cautious when it comes to that 'out' thing. I've learned that."

So yes, Peterson is listed as  doubtful for Sunday. And in Frazier's words, he is "very, very doubtful."

The head coach was asked directly what incentive there is to even consider playing Peterson as a 2-8 Vikings team has so little on the line against the Falcons.

"If he were at risk to himself, we wouldn't put him out there," Frazier responded. "And our medical staff along with what we observe with our eyes will help us in that determination. But we're not going to put any of our guys at risk health-wise or any other way."

As for the running back's mobility Friday with the boot off?

"The trouble he had was when he got up on his toes to plant or make a cut," Frazier said. "That's where he had trouble. That being the case it's doubtful he'll be able to get to the point where by Sunday we felt like he'd be able to get out there. But we'll see. The fact that he can put pressure on that ankle is a positive sign. He's made a lot of progress. But being able to cut as we all know is a major part of what he does."

And let's not forget:, while Favre started against the Bears in Week 15 of last season, he didn't finish, suffering an early concussion that knocked him out for good.