Oswalt and Prior were dominant when they got called up the first time.
A lot of it has to do with what division they are going to pitch in. I'm very high on Lincecum and not so high on Hughes.
"And so he spoke, and so he spoke, that lord of Castamere. But now the rains weep o'er his hall, with no one there to hear." - The Rains of Castamere