Kelvim Escobar is on the 15 Day Disabled list, retroactive to March 31st. Kevin Gregg is the likely 5th starter. It does not appear to be a big bad injury, just more like a strain to his elbow from overcompensating with that tired shoulder.
Escobar will likely (hopefully) just miss one start. His scheduled 2nd start would be April 15, the date he can at the earliest return anyway.