The reasons for the big line should be obvious--Buffalo's quarterback situation is unsettled right now. Rookie E.J. Manuel is recovering from a knee surgery, and the team isn't ready to say he's ready for Week 1. That leaves the starting job down to undrafted rookie Jeff Tuel throwing to an equally inexperienced group of receivers. Look for a heavy dosage of C.J. Spiller as the Bills try to take the heat off their young quarterbacks.
The Patriots have much more certainty at quarterback, though his supporting cast will be different. Tom Brady doesn't have Wes Welker, but he will try to recreate the receiver's production with Danny Amendola and Kenbrell Thompkins. Rob Gronkowski won't be playing, so look for rookie Zach Sudfeld to start in his place. The Bills defense is still shaky, so Brady's advantage is reflected in the odds line.
For more details on this matchup, check out Odds Shark.