Which NFL Running back should I use?

I can start two RBs, and I have: Earnest Graham vs Packers, Jonathan Stewart vs Falcons, Chris Johnson vs Vikings, Steve Slaton vs Jaguars. This is a non-PPR league, and 10 rushing yards = 1 point, so carries will be huge. Right now I am using Graham and Stewart, but I could see myself using Chris Johnson or Slaton also....Slaton is the only RB who is not in a timeshare, but he's an unproven rookie, and last week vs the Titans could be a fluke. Please help.