The NFL has four teams at 7-0 for the first time ever, making a league known for its any-given-Sunday parity perhaps the most top-heavy it ever has been.

So as the season reaches its midway point for those unbeatens, the New England Patriots are not the lone threat to go 16-0. What if it is, instead, the Denver Broncos, Cincinnati Bengals or Carolina Panthers who make the most sustained run at an unblemished regular season?

“In the league we try to create parity as much as we can,” said Steve Mariucci, the former coach of the San Francisco 49ers and Detroit Lions. “But boy, oh boy, it seems like the good teams are staying pretty good and the poor teams are having a hard time building it back up for some reason. But the Patriots look like they have a chance to go undefeated now and so do the Broncos. Peyton Manning looked great the other night. That defense is incredible. How they destroyed the Green Bay Packers, I didn’t see that coming.”

It is a highly unusual circumstance. The NFL never before had more than two teams reach 7-0 in the same season. That last happened in 2009.

The Patriots, in the season after DeflateGate, are the most obvious choice to duplicate their 16-0 regular season in 2007, when they steamrolled the rest of the league in the aftermath of the Spygate scandal. Those Patriots upped their record to 18-0 before being upset by the New York Giants in the Super Bowl, falling one agonizing step shy of joining the 1972 Miami Dolphins (who went 17-0) as the only perfect NFL teams.

Patriots quarterback Tom Brady again is having a most valuable player-caliber season with 20 touchdown passes, one interception and a passer rating of 115.8. He had 50 touchdown passes, eight interceptions and a 117.2 passer rating in the 16-0 season in 2007.

But the Bengals, with Andy Dalton, and the Panthers, with Cam Newton, also have quarterbacks who are in the league MVP conversation. Dalton has 15 touchdown passes, four interceptions and a 107.6 passer rating. Newton’s throwing numbers aren’t as dazzling with his 11 touchdowns, eight interceptions and a passer rating of 78.1. But he has run for 286 yards and four touchdowns. He has played with a recklessness that has stunned onlookers. Analyst Jon Gruden marveled during ESPN’s telecast of the Panthers’ overtime win Monday night over the Indianapolis Colts at the jarring hits absorbed by Newton while the quarterback showed a willingness to run over as well as around defenders.

Manning’s early-season struggles for the Broncos have been well documented. He has thrown 11 interceptions to go with his seven touchdown passes. But he is an all-time-great quarterback. And he summoned some of that greatness when he threw for 340 yards Sunday night in Denver as the Broncos knocked the Packers from the ranks of the unbeaten with a 29-10 triumph.

That is the sort of assistance that Manning must continue to provide to a Denver defense that is ranked first in the league. The Panthers also are ranked in the NFL’s top 10 in total defense, at 10th. The Patriots are 12th and the Bengals are 22nd in total defense. But Cincinnati and New England both are in the top-10 in scoring defense.

The Patriots and Bengals are in the top-six in total offense, while the Broncos are 17th and the Panthers are 19th. But Carolina is ranked fourth in the league in scoring offense. So the Denver offense, potentially just bolstered by this week’s trade for tight end Vernon Davis, is the only noticeable weak link among the offensive and defensive units of the undefeated teams.

Making a run at 16-0 also brings schedules, motivation and luck into play.

The Patriots must play at Denver on Nov. 29. The Bengals play at Arizona later this month and at Denver on Dec. 28. The Broncos, in addition to hosting the Patriots and Bengals, play at Pittsburgh on Dec. 20. The Panthers host the Packers this Sunday. Carolina also must play at New Orleans in December and still faces the Atlanta Falcons twice.

So there is plenty of sorting-out to be done with the now-unbeaten teams playing each other and facing other difficult opponents, not to mention the possibility of lurking upsets.

There also will be the question late in the season of what will — or won’t — be at stake if a team is closing in on 16-0 but already has wrapped up its playoff seeding. Not every coach would make the same choice that the Patriots’ Bill Belichick did when he played his starters against the Giants in a memorable 2007 regular season finale at the Meadowlands that set the stage for those teams’ Super Bowl rematch.

“It won’t happen,” one NFL coach said recently of a 16-0 season, “because it doesn’t matter to most teams. It’s not the ultimate goal.”

So even with four NFL teams sitting at 7-0, it remains a long shot that any will go 16-0. But it at least creates some intriguing possibilities.

“This is going to be really interesting with the Patriots going out in Week 12 to play the Broncos because both teams look like the real deal right now and of course, that’ll come to a head,” Mariucci, an analyst for the NFL Network, said in a conference call with reporters this week. “I mean, even these Cincinnati Bengals who are undefeated, when you look at their schedule, they look like they can go on a little bit of a run. They will play at Arizona in a couple of weeks and then they will play at Denver in Week 16. But the undefeated teams right now have a chance to have great records, great records going in there.”

More NFL