Theyre not trading one prospect for another.
Anyway, if Trea is in the deal, I expect more than Chapman or Miller.
The problem with having a premium prospect at an up-the-middle position is that everyone asks for him in every trade. There's absolutely no way he should be moved for a relief pitcher. Any relief pitcher. 60 innings of relief in one or two seasons at a fairly high salary is not even close in value to 6 seasons of SS or 2B with offense and even passable defense at minimum or near minimum salary. They'll want everything and a sandwich, just because they're the Yankees and they spend a lot of time sniffing their own jocks.
Suppose also this: you trade Turner to the Yankees. 2 weeks later, any one of Espinosa, Rendon, or Murphy gets hurt for an extended period (hardly a stretch, especially in Rendon's case). Suddenly you've got your closer...and Stephen Drew playing in your infield every day. Then you're f'ed every day of the week and twice on Sunday. So no. Absolutely not. Papelbon closing is better than even taking the risk of that happening.