This is more procedural than anything else, but it's worth noting that the Falcons have listed running back Steven Jackson as having a hamstring injury, not a thigh injury as was originally reported. Jackson still won't play this week against the Dolphins and could miss a few weeks.
Hamstring injuries can be very pesky and nag for a long time, so I would consider this slightly worse than a thigh injury.
Jason Snelling and Jacquizz Rodgers handle Atlanta's backfield for the time being. I think the guy I want is Rodgers, especially in PPR leagues. Snelling is a goal-line back, but he could have a hard time goiing anywhere versus Miami's rigid run defense. Meanwhile, Matt Ryan will probably be forced to throw a ton on Sunday, and Rodgers works very well as a receiver. In any case, both RBs are extremely low-end flex plays.