Which two running backs should I start this week out of these 3?

I would go with Mendenhall and Thomas. Mendenhall is a great pick for this week because KC has a terrible run defense, and Pierre Thomas is also facing the 2nd worst run defense in the league in Tampa Bay. Even though Williams has been on fire his last 4 games (488 yards, 3 TD's), he'll be facing a tough Miami defense this week. He's a worse pick than Pierre Thomas, though, who you can expect to bounce back from a couple of recent supbar games.