I did not post an in depth review, like I did for Randle, but I did watch all of McFadden's runs. What I saw was a runningback who lacked three very important things for the position:
1)Confidence. If you think Randle showed hesitation, McFadden will likely infuriate you. Whether it is scheme awareness or something else, he was tentative in his decision making.
2)Patience. He was took quick to run east/west and evetually wind up at the sideline or a Giants player. In a zone scheme, you have to have patience while also being decisive.
3)Vision. This might have a lot to do with the first two, and I know it is something Oakland people complained about for years, but if the hole isn't right in front of McFadden, he won't see it the majority of the time.
I know people saw a big back with lively legs and got excited, but that excitement has nothing to do with his play or production. That excitement is projection of his athleticism, a disdain for Randle and a the grass is greener attitude. I can post a write-up like I did for Randle, but I really don't think 6 carries warrants that.