Who to start at rb. only have 2 slots open...?

I feel the need to start jahvid best this weekend. I feel he will have a big hand in the shootout between Detroit and Chicago. Problem is right now I have Michael turner and Rashard mendenhall starting. Rashard playing a pretty good falcons defense and Michael playing a shaky pittsburgh dline but also a shaky o line in front of him. Informed answers only. Thanks s bunch guys...