Full freight on Espinosa, to me, would be a prospect in the 50-100 range and maybe a ML relief pitcher with a couple years of team control. Of course that sounds outrageous right now, which is why he won't be traded.
But why would the Nats trade him otherwise? If they think he's a distraction at the ML level with his "I wanna be the starter" business, he has two minor league option years left, and he'll have to nag pretty loudly to affect the Nats from Syracuse.