Ah yeah, riiiiiggght. There is a big difference between being serviceable and executing the position versus being a very good running back who has a profound impact on the game.
I give you a Shonn Greene vs. Marcus Coker comparison. At any point last year, did you feel Marcus Coker was a game changer...or at any point he could make the spectacular play to change momentum, field position, etc. No, he was mostly three yards and a cloud of dust. Even during the Minnesota game, he couldn't house any of those runs...and we settled or missed field goals...yet he had 250 yards so your first thought is how great he was. He didn't change that game. From my perspective, he always seemed to get the least amount of yards possible out of every run. I just watched the Michigan game again, and although we won, Coker couldn't get one yard in short yardage situations twice at critical times in that game. The oline got push, he just made the wrong move to get the yard...because his vision was terrible.
Now, contrast that with Greene. Teams game planned to stop him, he made the spectacular runs, hell, he made some spectacular 5 yard runs. Most importantly, he housed runs and he often made yards when there was nothing there. In stark contrast to Coker, he ALWAYS seemed to get the most possible yards out of every carry.
Not since the Wegher/Robinson combination, have we had backs that could help change a game...and provide the type of plays that kept drives going and put the kind of pressure on the defense that good backs do.
To me, this is what has been sorely missing in our offense the past two years. We don't have a game changer or special player at RB. Coker was not it and people in the know, understood it.