The Ravens enter this game as an underdog, but they are an elite group, and it will take a complete effort by the Pats to win and advance on Sunday. The last time these teams met in the playoffs—in the 2009 Wild Card round—the Patriots were embarrassed 33-14. Another performance like that one and they'll be on the outside looking in come Super Bowl Sunday.
But this year's incarnation of the Patriots are much improved over 2009's team. If they stick to the way they've been playing all season, the AFC Championship will be theirs.
Here are the four keys to a Pats victory and another appearance in the NFL's biggest game: