In his place will be rookie Tashard Choice and newly signed Alonzo Coleman. Choice, who has seen limited play this season, has done reasonably well with the chances he has received, averaging 4.9 yards per carry on 30 carries. Coleman, meanwhile, has never played in an NFL game.
While it certainly is not an ideal situation to miss your starting running back when playing the league's top defense, this may not be as bad as it sounds.
Pittsburgh has the number one rushing defense in the league, giving up a league-low 71.2 rushing yards per game, and only five touchdowns on the ground. Tampa Bay (1) and Baltimore (3) are the only teams to give up fewer rushing touchdowns than Pittsburgh.
It can be argued that, no matter who is in at running back, the Cowboys will struggle to move the ball on the ground. However, this does not mean that the Cowboys should abandon the running game altogether.
The last thing the Cowboys want to do against the Pittsburgh defense is to become one-dimensional. Instead, they will need to be creative.
Earlier this year, we saw sets that involved Jason Witten and Martellus Bennett in the backfield blocking for the running game. You can expect to see more of these sets this weekend. Screen plays and draw plays will also be important in establishing a good ground game with the young Cowboy running backs.
However, Marion Barber will not be missed the most in the running game. Tashard Choice was the ACC's leading rusher in his final two seasons with Georgia Tech. The kid can run. Perhaps the more pressing concern about Barber's absence this weekend lies in pass protection.
Pittsburgh's front seven is as good as they come. It will be up to Tashard Choice, Alonzo Coleman, Deon Anderson, Jason Witten, and Martellus Bennett to help fill Barber's void in pass protection. If they can do that, the Cowboys still have a great chance to upset the Steelers this weekend.