When Green Bay Packers LB Brad Jones tackled QB Brett Favre by the ankle on Sunday night, he fractured Favre's ankle in two places. After watching this video with Dr. Michael Kaplan, he explains that one is a stress fracture, and the other fracture is from a piece of bone torn off by a ligament, which is more like a severe ankle sprain. This is just my opinion, but I don't see how he can play on that ankle next Sunday. He could barely move after the Sunday night game, and this isn't something that can heal in six days.
And at this point, I don't see why it should matter if they go back to QB Tarvaris Jackson. Favre is playing so poorly right now that Jackson can't be worse.