Brian McTaggart tweeted (yesterday afternoon) that Wilton Lopez experienced some tightness and was "unavailable tonight."
To over-examine a tweet, "tonight" means that they're being precautionary with it, which is good. But it's obviously a troubling sign for the Closer-Who-Has-Not-Yet-Closed (a new category in ESPN Fantasy Leagues).
UPDATE: Zachary Levine updates this story, saying that he's available to pitch today, and that he just had a hard time getting loose before last night's game.
Also in the 2nd link, we find that there's no timetable for Jed Lowrie's return, and J.D. Martinez has been out with an elbow issue after he slipped in the dugout. If that's not the most Astros thing you've heard today, I can't help you.