Houston has 12 MLB caliber pitchers on their 40 man roster: Verlander, Valdez, Pressly, Abreu, Montero, Graveman, Javier, Brown, Urquidy, France, McCullers, and Garcia. But there are some issues:
Garcia and McCullers are hurt but expected back between July 1 and Aug 31.
8 of those 12 are starters. So if they keep the roster as it is then at least 2 guys are going to have to move into a bullpen role. Not necessarily a bad thing but probably not ideal. Houston might want to trade one of their SP for an elite RP if they can.
While all 12 guys certainly have a place on a big league roster, There are really only 2 sure-fire playoff-caliber SP (Valdez and Verlander) and 2 playoff-caliber high leverage relievers (Pressly and Abreu). Houston might want to replace 2 of their questionable SP for 1 proven playoff caliber SP and/or 1 proven high leverage RP.
The free agent pitching market is very deep this year. Some team is going to get a very good deal on a SP. Houston might be able to take advantage of that situation. I.e., if teams are all focused on Snell/Montgomery/Nola, a guy like Eduardo Rodriguez or Yariel Rodriguez might end up signing for far less than they’re worth and be a #2 guy for 4-5 years getting paid #4 salary. I like the idea of Houston adding a SP because I think a playoff bullpen of Pressly, Abreu, McCullers, Brown, Garcia, Graveman, and Montero would be badass, with a playoff rotation of Verlander, Valdez, TBD, and Javier (with France and Urquidy available for emergency starts or multiple inning relief appearances).