Uh-oh, folks. They’re at it again.

The franchise that has used your purple hearts as a trampoline since it was favored by 12 points in Super Bowl IV is back down on one knee. The ring box is open, the arm is extended and there’s a look of promise that maybe, just maybe, this time will be different.

At the quarter mark of the NFL season, the Vikings are the best team in the NFC, if not the NFL. The Broncos are the only other 4-0 team in the league, and, well, they did win the most recent Super Bowl. So let’s not get too greedy. Let’s rank the Vikings No. 2, assume they’ll beat Houston at home on Sunday, go 5-0 into the bye and then head to Philly (3-0) to decide whether Sam Bradford’s new team is better than his old team.

“We still got a long way to go,” coach Mike Zimmer warned after his defense’s latest beatdown, 24-10 vs. the visiting Giants on Monday night. “We’re not handing out any medals tonight.”

But, judging by the noise level inside U.S. Bank Stadium, fans are handing over their hearts to the league’s most surprising team. Again.

This is Charlie Brown running toward the ball with renewed trust. With a feeling that Lucy eventually will let him make contact after more than half a century of finishing flat on his back after yet another missed opportunity.

This is about blocking out four Super Bowl losses, Drew Pearson’s push-off, Darrin Nelson’s drop, Brett Favre’s interception, Gary Anderson going wide left and Blair Walsh going wider left. This is about enjoying the ride, even if the fans and the franchise end up clasping hands and driving off a cliff together like the final scene in “Thelma & Louise’’.

There are 12 more regular-season games left. That’s 720 more minutes of live NFL action for bones to break, ligaments to tear and bouncing footballs to ruin carefully crafted game plans.

So let’s not crown anybody. But let’s analyze three primary reasons the Vikings still are winning with complementary football after losing their young franchise quarterback, their Hall of Fame running back and their starting left tackle.

Quality and depth at corner

Saints quarterback Drew Brees was 35 minutes into his game against the Vikings at the Metrodome on Dec. 18, 2011. He had 24 completions and as many touchdown passes (five) as incompletions.

The Vikings were undermanned at cornerback and playing an outdated Cover-2 scheme under Leslie Frazier. Brees played only 47 minutes and still passed for 412 yards.

Today, the Vikings are overflowing five deep with quality corners. And those corners follow coach Mike Zimmer’s aggressive mandate to contest every throw.

That combination is the key to the Vikings running the gantlet of Green Bay, Carolina and the Giants while holding Aaron Rodgers, Cam Newton and Eli Manning to 14, 10 and 10 points.

The corners enable Zimmer to be, well, Zimmer. The corners make the team’s strength — its pass rush — a dominant weapon in an offensive-oriented league.

Ball security

People keep scratching their heads and asking, “What’s wrong with the Panthers?” Here’s what’s wrong with the Panthers:

They’ve turned the ball over 10 times in four games. A year ago, when they went 15-1, they turned it over only 19 times all year.

A month into the season, the Vikings offense still hasn’t turned the ball over. Only the Eagles can say the same thing, and they’ve played one fewer game.

Some of this is luck. But some of it is self-awareness by the offense, Bradford, Shaun Hill before him, and coordinator Norv Turner. They know, A, this team’s identity is defense and B, don’t mess up A.

Very special teams

When the Vikings were down 10-0 at halftime of the opener in Tennessee, Cordarrelle Patterson returned the second-half kickoff 61 yards to set up a field goal.

When the Vikings were down 10-0 in the first quarter at Carolina, Jeff Locke’s 62-yard punt set the stage for a safety, and Marcus Sherels returned a punt for a touchdown moments later. When the Giants pinned the Vikings at their 1-yard line early in the first quarter, punt gunners Patterson and Sherels caused and recovered a muffed punt, setting up a short field, a touchdown drive and a lead the Vikings never relinquished.

A fourth reason to buy into the Vikings could be unfolding at their new stadium.

“I thought the fans were unbelievable tonight,” Zimmer said Monday. “They had this place rocking.”

Whether the ending is good, bad or the typically painful, it’s clear that fans have handed their hearts over to the Vikings once again. Hang on, folks.