If the Astros continue to struggle, they could start to move some of their valuable pieces like Brett Myers and Wandy Rodriguez. I see Myers being the most likely of the two to be traded but Wandy could bring back more prospects.
Wandy is off to a slow start in 2011, but that should not alarm many people because he has done this almost every year of his career. The past three years, Wandy has had an ERA of 3.86 before the All-Star break and drops it more than a run to 2.80 after the All-Star break.
I believe these are five teams that would be interested in Wandy Rodriguez if the Astros decide to make him available later this year. These teams would be looking more long term than just a half year rental as Wandy is under contract for the next four years.