Well, we know, definitively, who's going down when Zimmermann comes off the DL. 
Mock is not looking good, but like Sportsfan observes, he does have good stuff and enough pitches to make it as a starter. McCatty has shown before he can get in guys heads and turn them around, so I still hold out hope he can get Mock through this adjustment period.
Admittedly it's looking like more of a longshot every outing, but still.
