I'm not sure what to expect from Karlos, first off, he is not even in training camp shape let alone game shape. I wouldn't expect him to hit the ground running in week 5. Gilleslee had a few great runs, but most carries for no yards, can't count on him for anything yet. Everyone else is unproven. We can't take chances on the RB position, it's too vital to the teams success. Bush seems like a safer bet short term than anyone else right now, training camp may change things, but for now it's the smart move.