MLBTR has a nice list of everyone who is out of options. This means that, if the Astros send them to the minors, then they have to clear waivers first.
Who's on this list?
Of this list, the only players who run the risk of getting sent down are really Arias and Sanchez. Of those two, would they clear waivers? Sanchez might, but I'm not so sure about Arias (though his injury may scare off enough teams).