Behind an improved offense, the Minnesota Vikings have their longest winning streak since 2005, but more importantly, they've been able to renew their playoff hopes.

Looking to build on that three-game run and help their postseason chances, the Vikings visit the slumping 49ers on Sunday as they try for their first win in San Francisco in nearly two decades.

The only playoff appearance Minnesota (6-6) has made in the previous six seasons came in 2004, but the team enters this weekend tied with Detroit and Arizona for the final NFC wild-card spot. Every opponent left on the Vikings' schedule currently has a losing record, following this trip to San Francisco (3-9) with home games against Chicago and Washington before closing the regular season at Denver.

Minnesota seemed to be out of the playoff picture after a 34-0 defeat at Green Bay on Nov. 11, losing star rookie Adrian Peterson to a knee injury en route to its first regular-season shutout loss in more than 16 years. The offense has responded since that defeat by outscoring opponents 112-49 as the Vikings have won three straight, including a 42-10 home victory over Detroit last Sunday.

"I just think we're focusing a lot more," said running back Chester Taylor, who had 70 yards and a touchdown on 14 carries in the victory.

"We're playing four quarters and just not stepping on our own feet and making mistakes that we used to make in the beginning of the season. We're just coming along as a team right now."

Taylor has run for 311 yards and five of his six touchdowns -- tying the career high he set last season -- during the Vikings' win streak, which is their longest since a six-game run from Nov. 6-Dec. 11, 2005.

"I would say that nothing wins like winning," Minnesota coach Brad Childress said. "You build on it, whether it is offense, defense or special teams and they all play off each other. ... It's amazing how much that adds a little hop in your step."

The Vikings won the first two games of this stretch without Peterson, but the NFL's leading rusher returned last Sunday to run for 116 yards and two touchdowns on 15 carries. Peterson is rushing for 119.7 yards per game -- 28 more than any other player -- and his 10 touchdown runs put him one behind San Diego's LaDainian Tomlinson for the league lead.

Behind Peterson and Taylor, the Vikings boast the best rushing offense in the league with 176.8 yards per game and an NFL-best 17 touchdowns. They'll oppose a San Francisco run defense which is among the league's worst, giving up 124.0 yards per game.

Emerging quarterback Tarvaris Jackson is coming off one of the best games of his two-year career as he completed 18 of 24 passes for 204 yards and two touchdowns. Over the past three weeks, Jackson has completed 77.6 percent of his throws (45-for-58) with three TDs and two interceptions.

Jackson had two touchdowns and five interceptions through his first five appearances of the season with just 600 yards passing and a completion percentage of 46.4.

"Just getting completions are big," Childress said. "You kind of underestimate that sometimes, but completions are big. ... I think I said it back during training camp -- the one thing you couldn't give Tarvaris was the turns, the experience."

Minnesota's offense is on a roll, but the defense also has improved, reducing its points and yards allowed each of the last three weeks. The Vikings have been very solid against the run all season and are limiting teams to a league-low 70.5 rushing yards per game, having held the Lions to 23 last week.

That unit now faces last year's top rusher in the NFC, Frank Gore. Gore, though, has only one 100-yard game all season.

That's one reason the 49ers are tied with Atlanta and St. Louis for the worst record in the NFC.

Minnesota, though, has lost eight straight in San Francisco, including three playoff games, since a 36-24 divisional playoff win there on Jan. 9, 1988. The Vikings lost 9-3 at San Francisco last season.

The 49ers, however, have lost four in a row at Monster Park to record their longest home losing streak since dropping five straight from Nov. 7-Dec. 26, 2004.

San Francisco has lost nine of 10 overall since starting the season 2-0, most recently losing 31-14 at Carolina last Sunday.

Trent Dilfer completed 14 of 29 passes for 171 yards and two touchdowns, but threw a career high-tying four interceptions.

"No matter how you lose, it rips your guts out," said Dilfer, who has a dismal 58.4 passer rating in six appearances this season. "I'm very disappointed with some of the mistakes I made."

Dilfer is expected to make his fourth straight start in place of the injured Alex Smith, and faces a Minnesota pass defense allowing a league-worst 278.8 yards per game.

It remains uncertain if Smith will return this season. He has missed the last three games with a shoulder injury, and it's possible he will undergo surgery.

"We'll have to see how this week goes as far as throwing and take it from there," Smith said. "The way everything's gone, I'd definitely like to come back and play this year."

The Vikings, meanwhile, will be without defensive end Ray Edwards, who has been suspended for four games for violating the NFL's policy on steroid use.

Edwards' replacement was expected to be Erasmus James, but the veteran was placed on injured reserve Friday because he needs surgery again to repair the ACL in his left knee. James only had returned last week after recovering from a torn ACL suffered in Week 2 last season.

Rookie Brian Robison and 2005 first-round pick Jayme Mitchell are expected to fill in.