I think there is something of a horse race between Mitchell, Chourio, Frelick, and Black. All of them could potentially stick if Black does enough to make Bauers go away, but outside of that the worst performing one likely gets sent down, though Chourio batting right handed makes that less likely if it is close. My guess is that Black probably goes back down. Perkins has just done too much to be in that category anytime soon. If Mitchell had Perkins OBP skills........