49ers defense keeps runners below average 49ERS

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In last week's loss to the 49ers, Detroit's running backs averaged 3.0 yards on 22 carries, never had a run of more than 9 yards and ... were thrilled with their production?

"That was part of the game plan, to be able to test them and just go out there and play Lions football," said running back Joique Bell, who had 14 yards on six carries. "We ran very well. That was the game we planned."

Huh?

Bell's sunny assessment in the aftermath of such a so-so performance is a reflection of the strength of the 49ers' run defense, which ranked first in the NFL last year and hasn't allowed a 10-yard gain to a running back in a 17-quarter, 78-carry span dating back to Jan. 1.

San Francisco's front seven appears to be just as stout this season, but it will get its first significant test Sunday when the 49ers visit Minnesota and Vikings running back Adrian Peterson.

A four-time Pro Bowler, Peterson has beaten the odds by returning 8 1/2 months after enduring a torn ACL and ruptured MCL on Dec. 24. In the season opener, he rushed for 84 yards on 17 carries and scored two touchdowns in a win against Jacksonville. His numbers (16 carries, 60 yards) declined in a loss at Indianapolis last week, but his knee felt better in the game's aftermath.

"It's night and day," Peterson said. "My body is feeling better. My knee is feeling better, less sore. Really, didn't experience any swelling last week or this week, so that's always a positive ... I woke up Monday with a smile on my face."

MINNEAPOLIS, MN - SEPTEMBER 9: Adrian Peterson #28 of the Minnesota Vikings runs against the Jacksonville Jaguars during NFL opening day September 9, 2012 at Mall of America Field at the Hubert H. Humphrey Metrodome in Minneapolis, Minnesota. The Vikings defeated the Jaguars 26-23 in overtime. (Photo by Andy King/Getty Images) less MINNEAPOLIS, MN - SEPTEMBER 9: Adrian Peterson #28 of the Minnesota Vikings runs against the Jacksonville Jaguars during NFL opening day September 9, 2012 at Mall of America Field at the Hubert H. Humphrey ... more Photo: Andy King, Getty Images Photo: Andy King, Getty Images Image 1 of / 3 Caption Close 49ers defense keeps runners below average 1 / 3 Back to Gallery

Peterson's expression might have changed after he studied the 49ers, who have stuffed the run this season despite being outnumbered up front.

In season-opening games against the pass-first Packers and Lions, the 49ers mostly played either dime (six defensive backs) or nickel (five) defense, which left them at least a man short up front. Still, they rank sixth in the NFL in rushing yards allowed (63.5) and eighth in yards per carry (3.2).

"It goes to show how good they are with their front seven," Peterson said. "It's not a surprise to me what those guys have been doing. They've been doing this since last year."

The 49ers have shown similar respect this week for Peterson, who, at 27, already owns the Vikings' career records for rushing yards (6,896) and rushing touchdowns (66). Peterson's nickname, "Purple Jesus," hints at his status, and 49ers coach Jim Harbaugh added to the mythology when asked about Peterson's sooner-than-expected return from reconstructive surgery.

"You're talking about one of the great, great athletes in the world," Harbaugh said. "And it's not going to be the normal person coming off of an ACL. He's one of these men who's in the National Football League, and they have superhuman powers of recovery."

Said All-Pro defensive tackle Justin Smith: "That guy's a miraculous healer. He's out there making cuts, looks just as fast as he ever has ... I know that all the work he put in during the offseason must have been ridiculous to get to where he is now. It's going to be a good challenge."

Unlike the season's first two games, the 49ers will have the benefit of defending the run with their base defense, allowing them to employ Isaac Sopoaga, their 330-pound line-clogging nose guard. Sopoaga, a starter, has played eight snaps this season.

In contrast to the Packers and Lions, however, the Vikings will match their strength against the strength of the 49ers' defense. Thanks to the presence of Peterson, Minnesota ranks first in the NFL in rushing yards per game (138.6) since 2007.

"I don't think they've played a team that's committed to running the ball like we will be," Peterson said. "But we know we have our hands full and we're looking forward to the challenge."

Rushing stats 75.7: NFL-low rushing yards per game allowed by 49ers' defense since the start of the 2011 season. 91.9: Adrian Peterson's career average for rushing yards per game.