I think the key to the Pats' Super Bowl run is how healthy the offense will be. That's not to dismiss the importance of Branch or Van noy, but the defense largely is what it is. I think Harrison could help get them off of the field on 3rd downs (which has been a problem at times this season) but I don't think the defense we see in the playoffs will be dramatically different from what we've been seeing. If the offense can get these injured skill position players contributing, it has a chance to be a much different unit from what we've seen the past month or so.
The intermediate passing game has been de-emphasized this season, largely due to the injuries to Edelman, Hogan, and Mitchell. If they can get even one of Hogan or Mitchell back and playing at a solid level, that could go a long way towards making this offense more difficult to stop. If they can get both of them back, the Pats will be an extremely difficult team to slow down. Without them, the Pats are basically limited to short throws to the backs and deep throws to Gronk and Cooks, with few threats in the intermediate passing game (Amendola, basically).
As for their potential opponents, it's a really weird set of teams this season.
Tennessee is garbage and it's a miracle they're even in the playoffs. The only way the Pats lose to them is if multiple disasters take place. I guess it's possible Mariota plays the game of his life but he has shown no reason to expect that to happen based on his body of work this season. I think they are easily the worst team in the playoffs, in either conference, and will probably lose by at least two touchdowns in KC this weekend.
Buffalo is a step above garbage but not that great a team either. However, as others have mentioned, their familiarity with the Pats could help them keep it close. And in a close game, all it takes a break or two to swing the outcome. I wouldn't lose any sleep about playing the Bills but I can envision a scenario in which they come into Foxboro and steal a W. Not likely, but possible. If McCoy is out then they go down into the garbage bucket with Tennessee and we're back to "it would take a miracle" status.
I think Jacksonville is being a bit overrated by some in this thread. The defense is supremely talented but they are far from a 2000 Ravens or 1985 Bears-type unit. Those teams had legit shutdown defenses where it was a mighty struggle to even move the ball. Stringing together a couple first downs and flipping field position would be considered a win against those teams. That's not really what this Jags defense is about. They basically live off of big plays: sacks, turnovers, defensive TDs. If you can avoid negative plays against them, there is hay to be made. And I'm still not sold on the Blake Bortles resurgence. He was horrible against a bad Titans team last week. Even if the Jags D forced a turnover or two, there's a decent chance Bortles would turn it over himself. Fournette hasn't really been all that impressive either. Keep him from breaking off a long run and he'll plod along for 3-4 yards a carry. It's not like he consistently rips off 10-20 yard runs with any regularity. This team had a pretty soft schedule and dominated a lot of bad teams. I think they're still a year (and an upgrade at QB) away from being a legit contender.
KC is a weird one to figure out. Won 5 straight to start the season, then lost 6 of their next 7 before closing out with 4 straight victories. Most of those losses were bad too: a 3-win Giants team; a 5-win Jets team; a 6-win Oakland team; a Bills team that had lost three straight and was going through a QB controversy (at home, no less). But even if they played at their best, I'm still not sure it would be enough to win in Foxboro in January. People talked about the opening game as if it was a blowout, but the Pats were actually leading going into the 4th quarter. KC reeled off a few big plays, NE couldn't move the ball, and the final score made it look like a blowout. But it really wasn't. In the end, I don't have a ton of faith that Andy Reid will coach this team up to bring their 'A' game to Foxboro, and I don't think those big plays would be there this time around.
And that brings us to the Steelers, the most legitimate competition for the AFC crown. Yes, they have always struggled against the Pats. But so did the Colts before they finally turned the tables. Previous performance is no guarantee of future returns, etc. And it's not like they got waxed this season, like they had in previous games. It was neck and neck all day long. This could come down to health. Again, will the Pats be healthy on offense? Will Brown be healthy for Pittsburgh? Also: how much of a distraction will James Harrison be for the Steelers? It was pretty obvious this week that it struck a nerve to some Steelers that he signed with the Pats. It's probably not going to amount to a material difference, but I think it's more likely to have a negative impact (however slight) on the Steelers than it is on the Pats. Think this matchup would come down to what most close NFL games come down to: who is healthier, who wins the turnover battle, and who makes the fewest mistakes.
I don't think the NFC is even worth thinking about at this point (vis-a-vis the Pats, at least) but I would probably be most worried about the Vikings. Keenum could turn into a pumpkin at any point in time but they have a great defense, a very good coaching staff, and the Super Bowl would be a home game for them. I may be splitting hairs though. As a group, the NFC playoff teams are much stronger than their AFC counterparts. I'm not sure anyone in the AFC outside of NE and Pitt would even qualify for the playoffs in the NFC. Maybe Jacksonville but they feasted on a bunch of AFC cupcakes. I'm still not convinced they're actually a good team.