How will Rosenfels do in Minnesota this season?

He's sitting on my bench in our dynasty fantasy league. We start two QBs each week, and since Favre retired (again) Rosenfels is going to fill that slot. I think this is my year to make a run, but I can't have Rosenfels flopping all season like he did against the Colts last year. I'm not sure whether to ride it out with him or try some blockbuster trade to get a better starter. And QBs DON'T come cheap in our league...