There are obviously more than two reasons why the Purple can win the game on Sunday. But two of the biggest (and I hope that Brad Childress realizes this while game planning) are Visanthe Shaincoe and Chester Taylor. I think they might even be the two most important offensive players on the field on Sunday, because the Eagles have struggled against similar players all year.
Philadelphia's strong against the run (3rd in DVOA) and strong against the pass (3rd in DVOA). Where they're weak, however, is against tight ends (19th in DVOA) and against running backs in the passing game (18th in DVOA). And this is borne out by more than just the advanced statistics. In each of the Eagles' losses, either a running back or tight end was their opponents leading receiver (except for their loss to the Ravens, where they turned the ball over 5 times, although a running back was their second leading receiver).
And it makes sense when you consider the way the Eagles play as well. This is a blitzing defense. When you're sending linebackers and safeties after the quarterback, you're removing the players that would normally be covering the tight ends and running backs. Also, you're forcing the quarterback to make quick decisions, which usually means they're going to throw their pass to a safety valve, which is usually either the tight end or running back.
So what does it mean? It means that Visanthe Shaincoe's emergence (he's currently second among Tight Ends in DYAR and DVOA) could be the single most important thing for the Vikings this Sunday. And it could mean that we see a lot more of Chester Taylor on passing downs (or, you know, if Brad Childress wanted to get creative, he could play BOTH Adrian Peterson and Chester Taylor on passing downs, though that's probably just crazy talk). And it means that, even though they're the best team in the NFL, according to DVOA, the Vikings have the weapons to exploit the Eagles defense.