Houston added right-handed pitcher Brandon Bailey, who was impressive during summer camp, to their Major League roster.
The Astros also recalled righties Cristian Javier, Enoli Paredes, lefty Blake Taylor, catcher Garrett Stubbs and infielder Jack Mayfield.
Right-handed pitchers Brad Peacock and Austin Pruitt, either of whom could have contributed to the starting rotation, were both placed on the injured list, along with right-handed pitcher Rogelio Armenteros.
The Astros will carry 15 pitchers and 15 position players on their Opening Day roster.
The players who did not make the roster, and the ones placed on the injured list, will report to Double A Corpus Christi, where they will continue training as part of the team's player pool.
A notable absence on the Opening Day roster is top pitching prospect Forrest Whitley, who entered summer camp in better shape than he did spring training.
Astros general manager James Click said Thursday he is not ruling out the possibility of Whitley contributing later in the season.
"We do have some guys who are a little short on experience, but they are long on talent, and we feel like that is going to play out in the long run," Click said. "In addition, given that there aren't going to be fans in the ballparks for a little while, it may actually be a little easier for these guys to make their Major League debut, or transition to the major leagues a little bit better than they can when you've got 40,000 or 50,000 people screaming at you.
"Ultimately, the decision was just based don talent the guys we thought could help us win."
Here is a look at the Astros' Opening Day roster:
Bryan Abreu
Brandon Bailey
Joe Biagini
Chris Devenski
Zack Greinke
Josh James
Cristian Javier
Lance McCullers Jr.
Roberto Osuna
Enoli Paredes
Ryan Pressly
Cy Sneed
Blake Taylor
Framber Valdez
Justin Verlander
Dustin Garneau
Martín Maldonado
Garrett Stubbs
Jose Altuve
Alex Bregman
Carlos Correa
Aledmys Díaz
Yuli Gurriel
Jack Mayfield
Abraham Toro
Michael Brantley
Josh Reddick
George Springer
Myles Straw
Kyle Tucker