Hank Conger, switch-hitting catcher, was traded from the Angels in exchange for Nick Tropeano and Carlos Perez earlier today. Perez had recently been added to the Astros 40-man - on the same day that Will Harris was claimed off waivers - so this represents a 2-1 swap in terms of the 40-man.
Pundits seem to think that the Angels have managed to fill a rotation need whilst trading their backup catcher (albeit one who received approximately 40% of the catcher plate-appearances for the Angels - second to Chris Iannetta) and getting their 2015 backup catcher back in Carlos Perez.
As for the Astros, my thoughts are that this trade will need to be evaluated at the end of the off-season. With Castro, Stassi and Corporan, along with Conger, all looking to catch - and none being consistently good enough for DH duties - then I would be stunned with one (more likely two) wasn't traded shortly.
The free-agent market is miserable for catchers this offseason, and therefore the Astros may be shopping Castro to whomever loses out on the Russell Martin sweepstakes. The Astros again deal from their perceived future-rotation logjam for a (possibly undervalued) major-league player whilst freeing up a 40-man slot. There are significant parallels with the Marisnick trade in this case as well.
This will make more sense when the next move happens, but I am picking that Castro and Corporan will be traded this offseason. This may, in turn, free up uniform-number-15 for Will Harris. Stay tuned.