Green Bay Packers head coach Mike McCarthy reacts to a call during the first half of an NFL football game against the San Francisco 49ers in Green Bay, Wis.

GREEN BAY — For the Green Bay Packers, the hope was that Cedric Benson quickly would add a new dimension to the offense and help revive a running game that often has seemed like an afterthought under Mike McCarthy.

The reality, at least in Week 1: Aaron Rodgers was the Packers' leading rusher in a loss to the San Francisco 49ers.

Benson had nine carries for 18 yards, averaging 2 yards per carry. Rodgers ran five times for 27 yards. Nobody else, including promising second-year back Alex Green, got a touch in the running game as the Packers (0-1) found themselves playing from behind.

"The way the game goes sometimes dictates whether you're heavy run or pass, but we don't want to be running the ball for 2.0 (yards per carry)," McCarthy said. "So that's not acceptable."

The Packers certainly aren't the first team to struggle to run against the 49ers. With a ferocious front seven, San Francisco was the NFL's stingiest run defense in 2011, giving up only 77.2 yards rushing per game.

But new center Jeff Saturday said the Packers can't just chalk their running game struggles up to playing a tough opponent.

"I think it's a little of both," Saturday said. "I think you kind of have the perfect storm — you've got a very good defensive front seven and guys (on the offensive line) who aren't oiled up exactly right. So then you get down and kind of become a one-dimensional football team, which played into what they want to do. It just kind of worked against us, the way we started."

Now comes a Thursday night game against the division rival Chicago Bears at Lambeau Field, with Benson getting another chance to face his former team.

The Bears (1-0) took Benson with the No. 4 overall pick in the 2005 draft, but his career in Chicago ended because he was inconsistent on the field and found trouble off of it. If Benson had any ill will toward the Bears, it has faded over the years.

"That was so long ago," Benson said. "I already got my shot at them a couple years ago."

Did he ever. With Cincinnati, Benson faced Chicago in 2009, rushing 37 times for 189 yards and a touchdown.

Benson acknowledged he did have some extra motivation that day.

"No question," Benson said. "That was the first time I saw them since we parted ways. And I wanted to have a good day."

After becoming a free agent at the end of last season, the Packers signed Benson early in camp.

It's safe to say the Packers won't give Benson anything approaching 37 carries Thursday — expect Rodgers to test Brian Urlacher's injured knee in the middle of the field — but when Benson does get the ball, he needs to do more.

Benson said his timing with the offensive line is coming around.

"I think we're there now," Benson said. "I think you're going to see a lot of progression."

Benson hardly took all the blame this week, as Packers offensive linemen acknowledged that they have to do a better job up front.

"The line's got to be better, getting movement and opening those holes up," right guard Josh Sitton said. "It was limited run snaps (Sunday), we got down and had to throw the ball. We're used to that. So when we do have those opportunities, we've got to take advantage of them."

But Sitton said the team also is looking for more out of its running backs, saying, "It's our job to move the defensive linemen out of the way. I think we need to improve on that, and I think the running backs need to improve hitting the holes and knowing which holes to hit and where to bounce certain runs and where not to."

Rodgers said better production in the running game — meaning more effective runs, not necessarily more running plays — will help open up the Packers' downfield passing game.

"We've got to do a better job," Rodgers said. "I think it's about making sure those runs are having more yards per attempt. The number of runs is not quite as important as making sure those runs are quality runs. That's going to help us loosen things up a little bit in the back end. When teams are giving us six-man box against our sub personnel, we've got to be able to run the football."