Why does Clinton Portis always trip

[Stacks42]

I was saying the same thing last night, Ive said it for as long as he has been here. He is a great back but once he hits the open field he stumbles. He had a long run last night where he started to stumble and in looked like he tried to run backwards, just looked strange.

I for one would like to see a few more plays where they let Portis run on the edges, get him outside. Running up the gut all the time is going to wear him down quickly