Not to mention obvious.
Stop Adrian Peterson.
"I think my primary concern, even if Ponder wasn't the quarterback, is to stop 28," nose tackle B.J. Raji said of Peterson. ‘Obviously, it's no secret, this will be Ponder's first start — that means no experience. But our main concern is Adrian Peterson."
In eight games against the Packers, Peterson has averaged 100.9 yards and 4.9 yards per carry with five touchdowns.
Since defensive coordinator Dom Capers arrived, the Packers have done a relatively good job of keeping Peterson in check. In four games, he's carried 92 times for 355 yards — a 3.9-yard average. That includes 14 carries for 72 yards in the Packers' 31-3 win at Mall of America Field last season and 25 carries for just 55 yards in a 30-23 loss in the dome in 2009.
"Mostly, just give the ball to A.P.," outside linebacker Erik Walden said when predicting the Vikings' game plan with Ponder making his starting debut.
The Vikings might be limping along at 1-5 but Capers didn't have to do much to capture his players' attention for this game against a downtrodden rival.
"What helps is the guys have a lot of respect for the guy (Peterson)," Capers said. "If you've seen the guy first-hand, he gets your attention. With our guys, when we look at tape in there, he gets their attention. When you see the plays he makes, I can hear them oohing and aahing when they're watching him. He has their attention because they're thinking about what we're going to have to do to stop this guy."
Stopping Peterson comes down to getting "all 11 hats around the ball," to use Walden's words. But it's more than that. It's about all 11 guys being in the right place.
"Run defense is like putting a glove on," Capers said. "Everybody's got to have their gap and you have to take care of your gap and you have to be disciplined because if you try to do too much and you get out of your gap, this guy will find it (snaps his finger). He's explosive enough to hit that open area."
Defensive end Ryan Pickett has seen the visual evidence plenty of times. Pickett arrived in Green Bay as a free agent in 2007, the same year the Vikings selected Peterson in the first round.
"You have to be real disciplined, especially playing against Adrian Peterson," Capers said. "You can't peek. If you've got a gap, you've got to stay in there because if you're peeking and you're out of your gap, he's going to hit that gap every time. The way he finds the hole, he's probably got the best vision for a running back that I've ever seen."
That means stopping Peterson comes down to playing defense as a team. It's about trusting that the defender in the gap next to you will make the play rather than jumping into that gap to make the play yourself. By vacating one gap for another, Peterson will use his incredible vision, bounce and acceleration to blow through the newly created opening.
That's where the greatness of Peterson gets in a defense's head.
"It comes down to trust," Pickett said. "Even though I might be able to get here, I've got to trust that my guy's going to be where he's supposed to be."
Which can be a challenge.
"Sometimes, because you're so eager to make a play," Pickett said. "That's what happens to a lot of people. They get impatient, especially playing against a good back like Adrian. As soon as you pop your head out of the gap, boom, he pops through there."
Peterson has the homefield advantage for this game, with the artificial surface only making him more explosive. In three games at home this season, he's averaged 106.7 yards and scored six touchdowns compared to 72.3 yards and one touchdown on the road. For his career, he's averaged 5.0 yards per carry in home games and 4.5 on the road. And in four career home games against the Packers, he's averaged 5.3 yards per carry.
"I like (the challenge)," Pickett said. "Yeah, I like the challenge. We love facing him. It's tough but it's a good measuring tool to see where we're at in stopping the run, because we know we're going to get it."
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Bill Huber is publisher of Packer Report magazine and PackerReport.com and has written for Packer Report since 1997. E-mail him at firstname.lastname@example.org, or leave him a question in Packer Report's subscribers-only Packers Pro Club forum. Find Bill on Twitter at twitter.com/PackerReport.