Helu was 55 best runningback recruit when he came out of high school. Sure he had talent, and so did Ameer. Helu and Ameer were sideline specialists, but when you needed the hard yard they didn't have the shoulders to carry the game. Get them into space on a flare pass and they shine. Dump the ball off underneath, they can weave for yardage. But imho neither guy inspired confidence between the tackles.
There was one year in the Big XII where Nebraska needed hard yards and fell short, 2010. Stats ran up in the non-conference were meaningless in the championship. We rode Suh not a runningback in 2010. And in 2012, Burkhead peaked while we went 5-3 in the B1G. As much as Burkhead was a robot making great running decisions, he was not a workhorse. When they leaned on him as a senior he broke.
To be a workhorse you run so rough and tough the defense has to commit to you with multiple players. The mark of a workhorse is carrying the rock behind your OL. It opens up the rest of the offense by sucking the D in tighter. Burkhead was a professional level decision maker that had ace quickness without a second gear. He was not a workhorse.