Alhough he could only wear shells and mostly just watch from the sidelines -- per the new CBA rules -- Cedric Benson was on the Packers practice field Monday, an emergency reinforcement for a depleted RB corps.

Benson, who agreed to a nonguaranteed, one-year contract Sunday, took part in some individual drills. He will not play Thursday against the Browns.

The eighth-year veteran, who’s coming off three straight seasons of more than 1,000 rushing yards and has missed just one game in the past two years, bolsters a backfield that is “down to three running backs,” as coach Mike McCarthy said Monday after practice.

Benson is 29, and after more than 1,500 career carries, it’s unknown how much he still has in the tank. To hear him tell it, though, he’s got plenty left.

"I've definitely got another 900-plus [carries]," he said. "I feel great. I do a good job of putting a lot of effort and taking care of myself off the field, and I think it contributes on the field. It's just kind of what you do. You grow older, playing the running back position, you understand the longevity of this position -- of any position in the NFL -- so you've got to do all you can to stay healthy.”

The Packers haven’t had a 1,000-yard rusher since Ryan Grant in 2009. Benson's goal is another 1,000-yard season, although it's unlikely in Green Bay’s pass-heavy offense.

"I definitely have a goal to still rush for 1,000 -- 1,000-plus -- and set up some big numbers," Benson said after practice Monday. "I understand it's not a run-first team, and the run is not real heavy here, but there's times where a back gets the ball 25 times. And I'm sure if things are rolling, the run game is set to a standard that we're hoping to achieve, it could be way more carries than that."

McCarthy commented on Benson for the first time Monday, saying that the veteran RB suited his team. “He’s been a very productive running back. He’s played in a one-back system the last few years, and it’s clearly evident that we’ve evolved more to a one-back system. I think he’s a good fit for our football team. I’m excited that he’s here.”

QB Aaron Rodgers deflected questions about why the Packers may have decided to sign Benson over Grant, the well-liked former Packer. Rodgers did say that Benson’s experience would be beneficial to the young RBs.

"It’s good for our team to have guys who have had success other places come here, add to the team, add some leadership to the team, some experience," Rodgers said. "I think it’s going to be a good transition for him. He’s in a spot where he can be around some other veteran players and have maybe more of a leadership role than he’s had at other teams. There’s high expectations for him, but we have no doubt he can come in and meet those expectations."

Kuhn injured: McCarthy was forced to cut practice 20 minutes short Monday night when FB John Kuhn suffered an ankle sprain. That left the walking-wounded Packers with three healthy RBs because Benson isn’t allowed to practice. Afterward, McCarthy vexed, “We’re down to three running backs and one of them, Alex Green, he’s obviously coming off major knee surgery. That’s why the last two periods were (cut). Right now, we have three running backs. We’ll see where John is the next couple days. I’d like to have four of them going into the game.”

McCarthy said the injuries have hindered his ability to properly prepare the team. "We’re not where we want to be. … Actually, the tempo was outstanding. I thought it was a heck of a practice just from an operations standpoint. When John went down, I just didn’t think it was worth the risk to try to get through the last team period with three running backs."

Rodgers lauds undrafted rookie: It's too bad that rookie free agent RB Du’ane Bennett hurt his knee and has been unable to practice. Rodgers, the reigning MVP, said he had a feeling Bennett would show his ability and impress coaches -- in Green Bay and elsewhere -- in the preseason. “I was telling Bennett, he was kind of my dark horse to lead the preseason in rushing," Rodgers said. "We always pick one guy who might play in the fourth quarter and pick up some yards. There have been guys in the past seven years who have put up some numbers. I thought he was a guy who could show some stuff late in games and get picked up by us or by another team. You feel bad for a guy like that." 

Bennett started 12 games for Minnesota in 2011 and led the team with 639 rushing yards and three TDs on 166 carries (3.8 ypc).

Injury report: LT Marshall Newhouse (concussion) and WR Tori Gurley (groin) returned to practice Monday. DT Ryan Pickett and S M.D. Jennings were excused for personal, noninjury reasons.

Still out were WR Shaky Smithson (ankle), WR Diondre Borel (groin), RB Bennett (knee), CB Davon House (shoulder), RB Brandon Saine (hamstring), FB Jon Hoese (hamstring), CB Sam Shields (elbow), RB James Starks (toe), ILB Desmond Bishop (hamstring), G Ray Dominguez (ankle), WR Greg Jennings (concussion) and TE Jermichael Finley (quadriceps). The four players yet to pass their physicals were also sidelined: DE Johnny Jones (knee), TE Andrew Quarless (knee), OT Derek Sherrod (leg) and OLB Frank Zombo (hamstring).

For up-to-the-minute Packers updates, follow James Carlton on Twitter at @CBSSportsNFLGB.