Not to sound like a homer but McGahee is a must start, simply because he is the featured back and does not split time like the rest of your backs. The second back is tricky. I would steer clear of Rhodes and Benson until they prove something this year, that leaves Bush, Maroney and Bell. All three will get their fair share of touches. Maroney looked great but it was against the Bills who could potentially have one of the softest run Ds in the league with the undersized defensive tackles. That leaves Reggie, who primed to score his first TD and there is no better place to do that than historic Lambo Field, but it is hard to ignore a Mike Shannon RB against KC. Tatum though will be all or nothing. He will either get you 150+ and 2 TDs or 10 yards on 4 carries.
If your a gambling man, I say Mcgahee and Bell. If you want to play it a bit safer, I say Mcgahee and Bush.