Focusing a little on the off-season in light of the Trade Deadline's...deadline this afternoon. Elias Sports Bureau ranks every player over a 2-year period and assigns a status based on their stats.
If a team offers free agent Player X arbitration, and he declines and signs with another team, then the team who signed him owes some draft picks. If Player X is a Type A player, the team who lost him gets that team's first-round draft pick from the team who signed him. It's one sandwich pick between the 1st/2nd round of the draft for a Type B free agent. This is an over-simplified version, because there are also considerations whether or not the team who signs the free agent falls in the 1st-15th picks of the draft, but that's basically it.
All this is to say that, for the Astros to trade an impending Type A free agent, they're going to want more than the equivalent to two of the Top 100 amateurs in the country. Then you get into the problem of offering arbitration, and the possibility of Player X accepting it (cough, Miguel Tejada, cough).
Where do the Astros' impending free agents fall (as of July 30)?