The 49ers' run defense ranked first in the league a year ago and is sixth through two games this season. But Vikings running back Adrian Peterson isn't ready to concede the ground game to San Francisco when the two teams meet on Sunday at Mall of America Field.

"These guys are good, but we're looking forward to the challenge," Peterson said in the locker room today. "I don't think they've faced a run-attack offense like we have. So I think that can switch things up. We're looking forward to playing those guys."

The 49ers held opponents to 77.2 yards rushing per game a year ago. Through a 2-0 start against Green Bay and Detroit, the 49ers are allowing 63.5 yards rushing per game.

The Vikings rank 14th in rushing with an average of 109 yards per game. Peterson ranks 15th in rushing with 144 yards on 33 carries (4.4).

"I'm sure they'll come in trying to stop the run," Peterson said when asked if he thinks the 49ers will play eight or nine players close to the line of scrimmage. "We have to be productive offensively to keep those guys honest. Complete some balls down the field and still run the ball. We have the guys to do it, and I feel if we're able to execute the game plan, then we should be OK."

Peterson has played the 49ers twice in his career. He has 88 yards rushing on 33 carries. As a rookie in 2007, he was held to 3 yards on 14 carries just five weeks after setting the NFL single-game rushing record of 296 against San Diego.

Peterson, however, is still excited to play the best the league has to offer at this point.

"Anytime we're playing one of the top defenses that stop the run, I'm even more stoked," he said. "I'm looking forward to it."

As for his health, Peterson still won't say he's 100 percent back from having his left knee reconstructed almost nine months ago.

"I feel there's another gear I can get to," he said.

Jared Allen also spoke to reporters today. Here are some highlights:

  • On 49ers left tackle Joe Staley: "He made the Pro Bowl last year, so it should be fun. I know him pretty well, so me and Joe will have a good day."
  • On 49ers running back Frank Gore, who ranks fourth in the league in rushing with 201 yards and a 6.1-yard average per carry: "Besides Adrian, he's probably tops in the league. They do some great things. They run the ball downhill. It's not like the Texans or the Colts, where they want to stretch you out and try to get the edges on you. They want to run downhill, in the `A' gaps and pick up five to whatever they can get. Gore does it great. He runs low behind his pads. He's patient. He knows where to get to."
  • On Antoine Winfield addressing the team earlier this week: "He's one of our leaders on the team, the oldest guy on the team, so what he had to say was very pertinent. It was good. And everyone agrees with him."
  • On his late hit on Andrew Luck on Sunday: "I'm not a dirty player. I play hard."