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The official attendance for the Vikings' opener Sunday: 56,607. Which means at least 50,000 people wandered into downtown Minneapolis in the late afternoon still in a daze and struggling to comprehend what all had happened.

Some left prematurely, shortly after Jacksonville receiver Cecil Shorts hauled in a 39-yard touchdown pass from Blaine Gabbert with 20 seconds left. After the two-point conversion, the Jaguars led 23-20 and the most impatient and cynical Vikings fans stomped out of Mall of America Field wondering why that bitter 2011 aftertaste was still lingering.

Another blown lead late?

Another home loss?

Was this yet another example of a bad team finding a new agonizing way to lose?

But then something crazy happened. Many things actually. And after Sunday's final play -- a wobbly Gabbert incompletion in overtime -- the Vikings had somehow stolen a 26-23 victory.

Just like that, a wave of euphoria washed away most of the displeasure.

It was that kind of unbelievable afternoon. So unbelievable, in fact, that the Vikings' final 12 points came off the foot of their rookie kicker, Blair Walsh, a calm and confident 22-year-old whose selection in the sixth round of April's draft raised a few eyebrows at the time.

But Walsh absolutely crunched a 55-yard tying field goal on the final play of regulation, then completed his perfect afternoon with a 38-yard field goal on the Vikings' first possession of overtime.

"His intestinal fortitude is incredible," coach Leslie Frazier said.

Added defensive end Brian Robison: "First NFL game. Rookie kicker. Game-winner. Game-tying kick. In my mind, he should definitely get a game ball."

And probably more than that.

Sunday's victory was so unbelievable that 48 hours after the Vikings finished their final practice of Week 1 insisting Adrian Peterson's availability would be a game-time decision, the eager running back wound up taking 17 carries, rushing for 84 yards and scoring both Vikings touchdowns.

Peterson was asked whether that sizable workload was more than he expected.

"It was less," he said, not kidding even a little. "I was ready to carry the load."

Later, Peterson was asked if he could handle even more work next week.

"Yeah. I'm feeling good right now," he responded. "My legs are loose. Seriously."

Really? The franchise running back is already feeling back to normal and producing like his old self barely eight months removed from major knee surgery? Yep, unbelievable.

Things were so unbelievable Sunday that Christian Ponder shook off an inexplicably lethargic start by the offense to deliver the biggest drive of his young pro career with little time and no margin for error.

It was a two-play march that required only 10 seconds. Ponder completed passes of 26 and 6 yards to Devin Aromashodu and Kyle Rudolph, respectively. And that put Walsh in position for the tying bomb as regulation ended.

"Even before we had to go out there," Ponder said, "I was telling guys that we're going to need our two-minute offense. I don't know that guys believed me. But I told them we had to stay in it. Fortunately they did and we were focused."

The Vikings made good on a handful of offseason promises during the opener. They promised Ponder would be better in Year 2. And after the Vikings dry-heaved their way to four punts on their first four possessions, Ponder responded by going 17-for-20 for 238 yards the rest of the way.

Six completions went to Percy Harvin for 84 yards, five to Kyle Rudolph for 67 more yards.

Peterson had promised since January that he had play in the opener. And he delivered, sending a jolt of energy through the Metrodome first with his introduction in the starting lineup and later by showing that brilliant burst-and-blast running style of his.

His longest run was a 20-yarder in overtime, allowing him to break Robert Smith's franchise career rushing record.

Said Frazier: "Some of those runs, I told Adrian afterward, 'I'm not sure you weren't just faking that ACL [injury].'"

That's not to say Sunday's victory was a masterpiece. Not by any stretch. There were the early defensive struggles, with Jacksonville delivering scoring drives of 17 plays and 77 yards and 11 plays and 78 yards early on.

There were silly penalties throughout.

And there was Shorts' TD grab in the closing seconds of regulation, with cornerback Chris Cook in coverage and unable to spin and locate the ball.

In a league defined by dramatic mood swings, a galling loss Sunday could have sent this mostly young, mostly unproven bunch staggering for quite a while.

Instead, a gutty rally and an improbable victory provided what the Vikings promised to deliver throughout 2012: resolve, toughness, rays of hope.

Dan Wiederer • dan.wiederer@startribune.com