Running back seems like the most replaceable position in all of football. Off the top of my head there is only one running back that isn't replaceable in the NFL and that is LT. Peterson seems like a good one but he is still young and has to prove he can stay healthy over a full season. I think drafting a running back in a early round is just foolish.
I think you go into camp with Perry (if affordable), Irons, Watson, and Dorsey. I also look at drafting a back with a later pick. I think an interesting guy is Slaton. I have a feeling his is going to fall pretty far in the draft and if you can grab him with a 4th pick that may be a good deal.