I think you're fine with Foster or McCoy, my personal choice is Calvin Johnson because I feel 100% confident I can get a blockade of RB in the middle rounds and play matchups well with 4-5 RB in my stable from rounds 4-12, including steals who should slot into 1st or 2nd round value.
Still, your best bet is almost certainly Foster or McCoy - outside of those two you're taking unwarranted risk and you better have a game plan