As long as he is healthy, Foster will get the majority of the carries. They've stuck with him through all those injuries for a reason. When healthy, and when given a good offensive line, Foster will do good. Look for that to happen this year.
I'd say the carry ratio is probably 55-45 (Foster-Williams) or maybe even 60-40 possibly.
Tony Romo Ben Roethlisberger
Marvin Harrison, Kevin Curtis, Patrick Crayton Roddy White
Frank Gore, Larry Johnson Marshawn Lynch, LaMont Jordan, Dominic Rhodes, Fred Taylor