One seemingly meaningless play stands as all the explanation necessary as to why the San Francisco 49ers were able to beat the Packers at Lambeau Field on Sunday.

Backed up to their four-yard line by a Tim Masthay punt in the third quarter, the 49ers faced second-and-15 from their 10. Running back Frank Gore then swept left end for 16 yards and a first down.

In a day and age dominated by passing stats, the 49ers are winning football games the old-fashioned way: They’re running the ball, which they did 32 times for 186 yards in their 30-22 win over the Packers.

It’s something they did well enough last season for it to carry them to the NFC title game. In their 2012 season-opening win over the Packers, however, the 49ers stirred in more passing and an avant-garde approach to offense that eluded them last season. Physical has been joined by finesse.

They used everything from an empty backfield look to a one-wide, two-back power formation. They threw on running downs and they ran on passing downs.

As a result of their dominant defense having been joined by an impressive offensive display on Sunday, the 1-0 49ers are almost certain to top the mythical NFC power rankings this week. They’re for real, folks, and they left the Packers hoping for a rematch with the 49ers later this season.

“It’s one game. This is a team that was in the NFC Championship last season. Hopefully, we’ll see them down the road in the playoffs,” Packers quarterback Aaron Rodgers said.

Forty-Niners quarterback Alex Smith didn’t steal the spotlight from Rodgers, but Smith was impressively error-free and more of a force in the offense than he was last season. He completed 20 of 26 passes for 211 efficient yards, two touchdowns and no interceptions. He was more than a caretaker or a game manager, he was a deciding factor.

He also plays on a team with potentially the best defense in the NFC, maybe in the whole league. It was a defense that sacked Rodgers three times, hurried him five times and defended the deep ball so well that it forced the best big-play quarterback in the game to live underneath the coverage.

“They played soft outside. They didn’t want to give up big plays,” Rodgers said. “They have a great defense. We didn’t have a chance to take a lot of shots downfield but, when we did, they made great plays.”

The point of all this love and respect for the 49ers is this: The Packers lost to a very strong team on Sunday. Losing to the 49ers is reason for neither disgrace nor despair. That’s not the same 49ers team the Packers beat in 2010. This is a more mature edition.

There’s also a lesson to be learned from Sunday’s loss to the 49ers: If you want to stand toe to toe with them, then you have to play as they play, and that means being able to run the ball and stop the run. The Packers did neither on Sunday.

“That’s for you guys to figure out,” Rodgers said when asked to confirm that theory.

The stats offer the confirmation. Eighteen yards rushing by running backs isn’t enough to force an opponent to respect the run. When your planned runs only gain 18 yards, you can tear the play-action pages out of your playbook. When you can’t run, you’ve been reduced to a one-dimensional attack, which is what happened to the Packers on Sunday, and that allowed the 49ers to drop seven and eight defenders into coverage and pin their ears back and rush with whatever was left at the line of scrimmage.

“They’re tough up front. We had some good looks to run the ball and didn’t get it done,” Rodgers said. “We have to play better next week.”

The 49ers made that fact crystal clear.

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