Which RB2 should I start in Week 1?

I have Pierre Thomas against the Lions, but it's looking likely he won't play due to a sprained knee. Someone JUST took Mike Bell from the waivers, so I have no choice but to use one of my backups to start this week. I have Derrick Ward against Dallas, Donald Brown against Jacksonville, Lesean McCoy against Carolina and James Davis against Minn. I'm thinking Donald Brown, especially since Ward is no longer the starter and faces a touch Dallas D. What do you think?