It seemed as if he was just starting to find a groove when his knee gave way on a tackle in the fourth quarter of the Cowboys' victory against the Oakland Raiders on Thursday.
Losing Dunbar means the Cowboys miss a speedy back who is a solid change of pace to DeMarco Murray's measured runs. Dunbar averaged 6.8 yards per carry, the biggest run coming on a 45-yard sprint, against the Raiders on Thanksgiving Day. Without Dunbar, the Cowboys will look at Phillip Tanner and Joseph Randle, two backs with similar styles to Murray.
The trio of running backs that are left don't possess Dunbar's speed, but are very quick.
"Well, I'd just say one thing: I'm proud of that offensive line," Cowboys owner/general manager Jerry Jones said after the Raiders game. "But [Dunbar] hit those holes quick. And you could see that, and then you could see him do that little move that he tries to coach up out there. He says that first move can kind of freeze them. That second one, they're going in the wrong direction. So, Dunbar, we're proud of him. I'm proud of him. He's a hard-working kid."
Durability is an issue with Murray and Dunbar, who have missed a combined five games this season due to injury. The running back position is so important for the Cowboys -- which makes finding one who doesn't miss games complex.
There are few running backs who can just stay on the field for every meaningful run. According to Pro Football Focus, Kansas City Chiefs running back Jamaal Charles leads players at his position with 687 snaps this season. Matt Forte of the Chicago Bears has played the second-most offensive snaps with 656, and he's been on the injury report with a balky knee.
Murray has participated in 470.
The Cowboys knew what they were getting with Dunbar, a speedy back who, along with some fumbling issues, isn't the most durable player in the world. Now they don't have him, and it's going to hurt in the final four weeks of the season.