There are a few good pitchers that have one year left on their deals. I don't think trading for a "legit number 1" is going to happen, but I think trading for a potential number 1 could be a good idea.
The Red Sox have a habit of trading young cost-controlled backend pitchers for stars. Masterson, Gabbard, Weiland, Arroyo come to mind. I can see a sign and trade centered around Doubront for a guy like Peavy, Johnson, Santana. Garza, Haren and Lincecum also have one year left before they hit free agency, but I don't think they fall into the same class right now.
The Sox should ignore Greinke completely, and take a hard look at Sanchez, Dempster, Mccarthy and Marcum.