The Astros outrighted Xavier Cedeno, Blake King, and Lance Pendleton off of the 40-man roster Wednesday. All three should be eligible to be minor league free agents this off-seaon.
Reports are showing King will be placed on the Corpus Christi roster. The Astros picked him up on waivers from St. Louis during the 2011 season, so I think he will be eligible to be a free agent after the World Series. I am researching this at the moment.
NOTE: Further research has helped me learn that Blake King is not eligible to become a minor league free agent. However, he is vulnerable to the Rule 5 Draft.
This move leaves the Astros' 40-man roster at 37.
Potential add-ons? Paul Clemens, Kody Hinze, Dayan Diaz would be my guess. If Jason Michaels becomes a free agent, this would leave one spot in the Astros' pocket for a Rule 5 selection.
Of course, the Astros will also eventually need to make room to bring back Jason Castro and presumably Brandon Lyon and Sergio Escalona, and maybe even Alberto Arias. All four of these players are currently on the 60-day disabled list and don't count against the 40-man roster.