Is Danks' velocity really down 2-3 MPH? If so, I say you give him the Baltimore start and maybe one after that before making a final decision. If that velocity doesn't come back, he's not going to be an effective 5th starter in the majors.
As far as contingency plans, I think Gonzalez deserves a second look. The end result was ugly yesterday, but the velocity was there for him and the periphials were ok. If things don't work out for him, Johnson should be next in line followed by Turner. I haven't seen any reports on his velocity since spring training, but if it has come back, I fully believe EJ can be a solid #5 starter. Turner has pitched the best out of minor league guys but doesn't have an option left, so when he comes up he's got to stick for good. I'd like to see him show success for a few more weeks before I consider, so maybe late May or early June.