The Astros will need to clear one spot on the 25-Man in the next 24 hours. Here are the possibilities I can think of:
a) Send Singleton back to Fresno. Lowrie will be getting time at the corners when he returns, and there's always Gattis and Carter getting time there, as well.
b) Send Hoes back to Fresno. Gattis will just have to play LF every now and then, and with Tucker, Marisnick, and Rasmus situated in the outfield, Gattis can act as a 4th OF if needed.
You probably want something done with Tony Sipp, but that's not going to happen as he's the only lefty reliever now that Thatcher's gone.
There are other possibilities, but these are the three - and two of them are going to have to happen - that stand out to me. Remember, the Astros need one 40-Man spot, but two 25-Man spots. We're also not mentioning the possibility that spots open up with trades over the next eight days.