Oh I don't want to "dump" Yorke. But where the Red Sox want to be as a franchise is to identify the prospects who are desirable but tradeable. I know it's annoying - but let's use the Dodgers example. The Dodgers were able to trade Alex Verdugo - a perfectly good starting outfielder prospect, to the Red Sox without thinking about it. Yes, they got a superstar in return ... but that is kind of the point. You'd like to be in a position to have good players to deal while keeping your true star ceiling clean as much as possible.
On the Sox farm, I think you identify Mayer (struggling at AA, but also one of the youngest regulars in that league), Anthony (with the leaps he has made and his tools) and Bleis (the tools again) as the sort of star ceiling you want to hang on to. I could be wrong of course - but we are dealing in probabilities here.
Ultimately I don't want to deal any of these guys unless a good player with substantial team control is coming here.