According to Ken Rosenthal, the Astros reached out to the Brewers sometime in January to discuss the possibility of a trade for Jonathan Lucroy.
As Rosenthal notes, their incumbent starting catcher, Jason Castro, is set to hit free agency after the 2016 season, and given his elite skill set in terms of pitch framing, he'll likely be a highly sought after commodity. They do have Max Stassi backing up Castro on the depth charts, but he's been unproductive in AAA for two consecutive seasons, and it's fair to question his value moving forward.
He's had three stints with the Astros, but he's accumulated just 45 plate appearances thus far. FanGraphs rates his future value as a 40, but according to their scouting reports, he doesn't really figure into Houston's future.
"Stassi completely stopped hitting in Triple-A, and is now an afterthought in the Astros catching plans. Stassi still has a touch of power, but not much else. It's unlikely he'll ever get on base enough to be more than a light-hitting backup."
If the Astros can't work out a trade for Lucroy, or another player entirely, and are unable to retain Castro in free agency, they'll have two options; sign a different free agent, or move Evan Gattis back to catcher. A.J. Hinch mentioned the latter as a possibility, and we could even see it this year.
AJ Hinch on Evan Gattis: "I haven’t given up on reintroducing catching to him once he gets healthy."— Evan Drellich (@EvanDrellich) February 21, 2016
As for the free agent class of 2016-2017, there are a number of options that will be available. Alex Avila, possibly Francisco Cervelli, Dioner Navarro, Wilson Ramos, Jarrod Saltalamacchia, Geovany Soto, and the likely jewel of this group, Matt Wieters.
The Astros will certainly have a number of avenues to explore as the season progresses, and there's always still the chance that they could revisit their talks on Lucroy as the trade deadline gets closer.