So this is what momentum is supposed to look like. You wouldn’t have noticed from the atmosphere in the Metrodome as boos echoed from the once-torn roof every time Donovan McNabb threw an incompletion during Sunday’s 34-10 win over the Cardinals.

Despite improvement in several areas, there’s no denying the Vikings are the NFC North’s worst team on paper, with some of the same problems bubbling to the surface for the fifth consecutive week.

Fair enough. But even as the Vikings led by 21 points late in the game, it shouldn’t have felt like they were down 10.

Maybe the Vikings must regain the fans’ trust after the way the first month of the season unfurled.

“You expect it when you’re 0-4 (for the fans) to tell you exactly how they feel,” linebacker Chad Greenway said.

Sunday was a starting point to reconciliation, but the Vikings haven’t had trouble starting this season.

After their 28-0 first-quarter explosion, which tied a franchise record for points in a quarter dating to 1986, the Vikings were on their way to a numbing 89-19 advantage through five first halves this season. Running back Adrian Peterson (29 rushes, 122 yards) ripped through any defender in his way to three first-quarter touchdowns, tying his career high for a game.

The score was 14-0 with 8:55 left in the first quarter, and McNabb hadn’t even completed a pass. McNabb could thank Peterson, an opportunistic defense and good field position for that.

After the Vikings failed to record a takeaway in the previous two games, cornerback Asher Allen and safety Jamarca Sanford combined for three interceptions, and the defensive line flustered quarterback Kevin Kolb all game.

Defensive ends Jared Allen and Brian Robison had two sacks apiece, and Robison forced a fumble that led to a first-quarter touchdown.

The secondary bottled Cardinals’ Pro Bowl receiver Larry Fitzgerald (four catches, 66 yards) despite the absence of Pro Bowl cornerback Antoine Winfield because of a neck injury. Allen, Chris Cook and Cedric Griffin took turns jamming Fitzgerald at the line and forced the Cardinals to attack over the middle with tight ends, to mixed results.

Even the Vikings’ offensive line, which has struggled at times this season, handled the Cardinals’ 3-4 front and imposed its will with the running game in the first half.

But the spotlight still was placed directly on the passing game, which has struggled with or without the inactive Bernard Berrian.

Take away McNabb’s 60-yard gain to receiver Devin Aromashodu midway through the third quarter – an impressive across-the-middle throw, to be sure – and McNabb was 9 of 21 for 109 yards.

He was 3 of 10 on third down while routinely missing receivers short on short or intermediate routes – sometimes 5 or 6 yards short. Cardinals defenders dropped what should have been two easy interceptions.

Percy Harvin, the Vikings’ top receiver, was targeted twice and caught one pass for 12 yards.

“There is no go-to guy right now,” McNabb said. “We’re all still getting comfortable in this offense and working on each other’s timing and chemistry.”

The running game suffered as a result, despite the first-half explosion. Peterson rushed 16 times for 36 yards in the second half, staying true to his second-half production of less than 3 yards a carry for the season.

“We’re not going to wave a magic wand and all of a sudden have a great offense,” Harvin said.

The Vikings will savor this win knowing how ugly things would have gotten if they faced the teeth of the NFC North schedule – at Chicago on Sunday, hosting Green Bay on Oct. 23 – coming off six straight losses dating to last season.

“I don’t know what the mentality of this team would have been,” Cook said. “This is definitely a big ego boost.”

That the Vikings protected a lead is a positive step. Minnesota can add to its win total if the defense replicates its performance against Arizona.

The Vikings held Kolb to a 46.9 passer rating and running back Beanie Wells to 3 yards a carry.

Coach Leslie Frazier delivered a simple message to his team at halftime: “If we sincerely want to achieve our goals, it’s there for us to get it done. We can’t allow ourselves to be denied.”

In the game’s final minutes, Allen and defensive tackle Kevin Williams tried to loosen up Frazier by patting him on the back and playfully squirting water on his shoulder with a Gatorade bottle.

For once, the entire Vikings sideline could exhale.

“We played well enough to win the game. That’s all you can ask for,” Harvin said. “We all just wanted to get one. Once you get one, you can go from there.”