Going undefeated through a 16-game NFL schedule isn’t just difficult. It’s pretty much unheard of. The Miami Dolphins started all of that undefeated chatter back in 1972 when they went 14-0 in a 14-game regular season and then won three playoff games (including the Super Bowl) to go 17-0 and give the league it’s first (and only) undefeated run.

The 2007 New England Patriots bested them in two regards, as they played two more regular season games (16-0) and tacked on two playoff wins to give the league it’s best perfect run in a season in history (18-0). The problem? They didn’t finish the job, as they fell to the New York Giants and weren’t so perfect in the end with an 18-1 record.

Still, these two teams did accomplish perfection during the regular season and while they did it in two different formats, they’re still the only teams to ever get it done. Each year NFL fans ponder whether or not it can be done again. This year we have a ridiculous FIVE undefeated teams as we gear up for week six. Check that: four, now that the Atlanta Falcons lost to the New Orleans Saints on Thursday Night Football.

But four remain. We have the defending Super Bowl champion New England Patriots, the upstart Cincinnati Bengals, the Denver Broncos, the Carolina Panthers and the Green Bay Packers.

So, which one has a realistic shot at running the table? Let’s break each team down:

New England Patriots

New England absolutely has a shot and they probably have the best chance. Not only are they the only team ever to go an entire 16-game season without a loss, but they also just won the Super Bowl last year. On top of that, Tom Brady and co. have clearly looked to be on a mission thanks to everything that came with the deflategate scandal. It wouldn’t be all that shocking to see another 16-0 run just to shove it in the face of the league. It’s not necessarily likely but it wouldn’t be overly surprising.

Cincinnati Bengals

The Bengals are on quite the roll to start off 2015, but it’s very difficult to see them going the entire year without a loss. Schedules be damned, they’ve survived at least two close calls to get to this point and an Andy Dalton-led team is never easy to trust. Cincinnati looks like a bold, new version of themselves and I can see them going 13-3, winning the AFC North and maybe even finally winning a playoff game again. But going undefeated? That’s just not in the cards.

Denver Broncos

The Denver Broncos have almost no chance of going 16-0 this year, unless the Peyton Manning of old suddenly shows up. Manning has been a shell of his former elite self, unfortunately, as these Broncos have relied heavily on the league’s best defense. They can’t run the ball, their offensive line is banged up and Manning looks the worst we’ve ever seen him. They’re still probably good enough to take the AFC West and maybe make a run in the playoffs, but they’ll still lose a few games during the regular season.

Carolina Panthers

Cam Newton has been impressive. He’s helped the Panthers to a 4-0 start for the first time in years (the last time they did that, they made it to the Super Bowl), and he’s done it without an effective running game or a star wide receiver (Kelvin Benjamin is out for the year). They’ve also done it against nobody yet, too. Carolina has had some close calls and none of their games offer a trademark win against a really tough opponent. Beating the Seahawks in Seattle this week may classify, but that’s pretty unlikely. And there’s the argument against them. Just like Atlanta fell this week, the Panthers are soon to, as well.

Green Bay Packers

Green Bay is the only other undefeated team on this list besides New England that could make sense at 16-0. But they’re not getting there, either. Their offense is finally starting to show how badly they miss Jordy Nelson’s ability to stretch the field and produce big plays, while there are major questions in the ground game, as well as Green Bay’s inconsistency against the run, defensively. There are pieces here to suggest a Super Bowl contender resides in Wisconsin, but running the table is crazy talk. They have some solid wins under their belt, but they have some tough battles ahead and have enough flaws to easily assume they won’t make it through the next 11 weeks without at least one hiccup. I can see an epic 14-2 season on the horizon, but the Pack will falter at least once or twice before the season is up.

There you have it. The undefeated teams of 2015 are all impressive in their own way and all are near-locks to make the playoffs and possibly even make some noise. But if we’re being realistic, the only team that looks the part of a potential undefeated squad is the Patriots.