The Vikings led the NFL in run defense the past three seasons, the first time any team has accomplished that since the 1970 merger. But they enter Sunday's game against the San Francisco 49ers ranked 15th in that category after two less-than-stellar performances against the run.

That's been one of the biggest surprises from their 2-0 start and it's something the players vow to address this week. "I think sometimes we get in this mode that everybody wants to make a play," linebacker Ben Leber said. "You've got to be happy that guys want to do that but sometimes we're getting out of our gaps that we're supposed to be in and guys are trusting that you're going to be there. Those one or two missteps will hurt you, so I think we need to sit back and get back to fundamentals and understand it's a team defense." The Vikings say they are not surprised the Cleveland Browns and Detroit Lions tried to attack them on the ground despite their history of stopping the run. "You're the champ. Doesn't everybody go towards the champ?" defensive end Ray Edwards said. "Of course they're going to come and try and run the ball on us and see if we got lackadaisical in that spot. Now we just have to buckle down more and show who we are and what we do." They will get a tough test with 49ers running back Frank Gore, who rushed for 207 yards Sunday against the Seattle Seahawks, including touchdown runs of 79 and 80 yards. "It's a huge challenge," Leber said. "We've proven that in the last few weeks we can be a little leaky in the run game and we're going to shore that up this week. But he's a top, elite back in the league and we're going to really have to be on our P's and Q's and watch a lot of film and make sure that we can get a lot of guys on him at all times." The Vikings have not allowed a 100-yard rusher in 25 consecutive games -- the second-longest current streak behind the Baltimore Ravens at 36. Their opponents averaged only 70.8 yards rushing per game the past three seasons combined. The Lions rolled up 94 yards on the ground in the first half Sunday. Defensive end Jared Allen blamed missed tackles as a primary cause for the inflated numbers. "You have to make tackles," he said. "That's all it is. We missed some tackles in the first half that we made in the second half. That's the bottom line. We make those tackles and it's a different stat line."