The Astros added right-hander Rogelio Armenteros, catcher Garrett Stubbs and left-hander Bryan Abreu to their 40-man roster ahead of Tuesday's deadline to protect players from the Rule 5 Draft.
Armenteros, 24, is Houston's No. 12 prospect per MLB Pipeline. He spent the 2018 season with Triple-A Fresno, posting a 3.74 ERA in 22 appearances (21 starts).
Stubbs, 25, is the Astros' No. 15 prospect. He hit .310/.382/.455 in 84 games for Fresno last season.
Abreu, 21, posted a 1.49 ERA and 1.03 WHIP in 14 appearances (seven starts) between Class A Tri-City and Class A Advanced Quad Cities, striking out 42 percent of the batters he faced.
The Rule 5 Draft takes place on Dec. 13 on the final day of the Winter Meetings in Las Vegas. Players who signed with their current club at age 18 or younger and have played professionally for at least five years are eligible to be selected, as are those who signed at 19 or older and have at least four years of professional experience. Clubs pay $100,000 to select a player in the Major League phase of the Rule 5 Draft. If that player doesn't stay on the 25-man roster for the full season, he must be offered back to his former team for $50,000.