Brandon Jackson doesn't have an established track record of consistent production like the player he's replacing. Still, the Green Bay Packers are confident he can carry the load in the wake of Ryan Grant's season-ending ankle injury.

And if Jackson can't stay healthy, things really get dicey.

The Packers kept only two true halfbacks, Grant and Jackson, on their 53-man roster coming out of training camp. With Grant gone, Jackson's main backup and the Packers' primary third-down option for the time being is John Kuhn — a fullback who has shown enough ability with the ball in his hands to become an insurance policy.

"It's one of those things where you work on it in the preseason as an emergency-type situation, and now it's an emergency," Kuhn said. "We need to go out and perform."

Going into Sunday's home opener against Buffalo, some might see a team with Super Bowl aspirations suddenly being one injury away from having a fullback as their No. 1 running back — especially after Jackson has missed time with injuries in each of the past three season.

Packers coach Mike McCarthy considers Kuhn more than just a fullback. McCarthy says Kuhn, who was a record-setting rusher at Division II Shippensburg University, has plenty of experience in the Packers' one-back offensive sets.

"The one-back position carries fullback and halfback responsibilities, and we're prepared to go forward," McCarthy said. "So I don't look at us as one play away from being locked into playing with a different position at the (halfback) position of our offense."

Backup plans aside, Jackson is confident he can carry the load. A second-round pick out of Nebraska in 2007, Jackson has become an effective third-down back.

"They've always been telling me you're one play away, and just be ready," Jackson said. "Obviously I've been doing that for three years now, a long time coming. And it's here, and I'm taking advantage of it."

The Packers did add depth this week, signing relative unknown Dimitri Nance off the Atlanta Falcons' practice squad. Nance, who went undrafted out of Arizona State, describes himself as an inside runner with an ability to break tackles and catch passes.

"He is actually someone that we were looking at through training camp," McCarthy said. "I just had a chance to watch him today. Very explosive, instinctive, definitely has a very strong, quick lower half. Everything we saw on film was validated today. He is a young player and I think he will be a good fit for us."

And there has been speculation that it might make sense for the Packers to trade for a running back — including a potential move for a player they'll face Sunday, the Bills' Marshawn Lynch.

Packers quarterback Aaron Rodgers, who played with Lynch at Cal in college, would be all for it. Asked what he would say if the Packers' front office asked him about Lynch, Rodgers responded, "bring him on."

"I think when you give a guy a change of scenery, and a guy like that who might feel like he has something to prove, and surround him with two guys, (linebacker Desmond) Bishop and myself, who have played with him, I think that can only help him feel comfortable and see a lot of production," Rodgers said.

But Packers general manager Ted Thompson isn't known for making splashy moves out of desperation and doesn't like to part with future draft picks. So for now, it's Jackson, Kuhn and Nance.

Grant was not present when the team's locker room was open to reporters Wednesday. On his Twitter account, Grant said he felt like he had a chance of returning later in the season but understood that the Packers needed the roster spot.

"You can sit here and say he would have been ready for the playoffs based on someone else that went through it in the past," McCarthy said. "You look at past injuries, but it's all about the individual. It's about the doctor's opinion of the specific injury."

And while Grant had been remarkably durable for the Packers until now, the same can't be said for Jackson.

He missed four straight games with a shin injury in 2007, two games in 2008 with a wrist injury and the first four games of last season because of an ankle injury.

Beyond that, Jackson hasn't carried the ball more than 75 times in a season — so how much will he have left in December, when Grant seemed to be at his best?

"This offseason I trained my body to handle the load and obviously it's here right now," Jackson said. "So we'll see."