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The Arizona Cardinals and the Minnesota Vikings were two of the biggest surprises in the first quarter of the season, two franchises believed to be in rebuilding mode before incredibly fast starts thrust them into playoff position.

When the 4-2 teams meet on Sunday at the Metrodome, the outcome could go a long way toward helping one team stabilize after a stumble and send the other into a downward spiral that may be difficult to overcome.

The Cardinals started 4-0, with a stunning victory at New England going a long way toward establishing them as playoff contenders. They also beat the Seahawks, who have emerged as legitimate playoff hopefuls in the early going, and the struggling Philadelphia Eagles, all quality wins that raised expectations for the season.

But they've lost two in a row, at St. Louis and home to Buffalo, and quarterback Kevin Kolb is out indefinitely with rib and chest injuries. That means John Skelton, who won the job in preseason, will make his start since spraining his ankle in the opener. He'll face an improved Vikings defense, trying to jumpstart an offense that has scored just 19 points in the last two games.

"We have a lot of issues that we're working on offensively to get a little better at," Cardinals coach Ken Whisenhunt said. "I hope that we can do that. We're going against a good defense this week."

A defense that is looking to bounce back after getting stung by Robert Griffin III last week. The Vikings won four of their first five games, riding a stingy defense and Percy Harvin's all-around brilliance to the top of the NFC North.

With Christian Ponder in his first full season as a starter and young players all over the secondary, most observers expected the Vikings to need at least another season of grooming before they were ready to return to contender status. But wins over San Francisco at home and Detroit on the road have raised hopes among fans that two straight last-place finishes were all they were going to have to put up with.

But Ponder has turned the ball over five times in the last two weeks and RGIII had the defense completely out of sorts last week in a 38-26 victory.

Now the Vikings enter a crucial stretch with two games in five days — next week they host the Buccaneers on Thursday night — before the schedule starts getting tougher.

"We've got two home games in a row and you never want to lose at home, so that's the biggest deal," Vikings defensive end Brian Robison said. "We want to win these next two games, hopefully be at the halfway point at 6-2. But the bottom line is we can't get that done if we don't beat Arizona this week."

The Vikings can take solace in how they responded to their only other loss of the season. After dropping a Week 2 game at Indianapolis, Antoine Winfield addressed the team to try to insert a sense of urgency and renewed focus into the group. It worked beautifully, with the Vikings ripping off three straight victories before losing to the Redskins.

"Just as you grow as a team as the season goes on, I think our guys know how important it is to focus in on this next opponent and you have to move away from what has happened previously, win or loss," Vikings coach Leslie Frazier said. "We've done a pretty good job. I think we have moved on."

Ponder is trying to recapture the mistake-free form he exhibited earlier this season, but he'll have his hands full doing that against the aggressive Cardinals defense. The Vikings expect to have deep threat Jerome Simpson back after missing last week with a back issue, and he could help loosen the defense up after they saw the Redskins crowd toward the line of scrimmage to take away Harvin and Adrian Peterson, who expects to play with a sprained left ankle.

Ponder has been concentrating on his footwork in practice this week and stepping up in the pocket rather than looking to scramble too soon.

"It's not really decision making. I'm not making bad decisions," he said. "It's something that is easily correctable. I think a lot of it has to do with my footwork and it's something I'll work on this week."

The Cardinals need this one just as badly as the Vikings do as they try to keep a two-game skid from turning into something much worse. They host the San Francisco 49ers next week before trips to Green Bay and Atlanta sandwich the bye week.

"We know we are a good team," linebacker Daryl Washington said. "We know we can play well any week. We just have to continue to execute and stick to the plan."

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