Here's the thing about this rotation. They have looked bad, but their peripherals show that they have not been nearly as bad as their ERAs indicate, especially Clay. They will get better. It's almost impossible to sustain an underperformance of your xFIP by more than one run.
Compare each starter's ERA to his xFIP:
Clay ERA 6.03, xFIP 3.10
Kelly ERA 5.72 xFIP 3.27
Porcello ERA 4.38 xFIP 3.72
Miley ERA 7.15 xFIP 5.15
Masterson 5.18 xFIP 4.89
We should see significant improvement from Clay, Kelly, and Miley, and modest improvement from Porcello. They still won't be a great staff, but they will be better than what we've seen. They should be middle of the pack. The fact that they're all underperforming their peripherals is an enigma.