For some time now, the Houston Astros' best path towards addressing their rotation has been through the trade market. They probably would have preferred to keep Framber Valdez since they didn't trade him or sign another of the top free agent arms, but they simply don't have the payroll space to do so as long as Jim Crane views the CBT as an upper bound. One name that recently popped up on the Astros radar is Mike Burrows and things have escalated quickly since then.
Details are still iffy at the moment, but it appears as though the Astros are deep in talks on what wil end up being a three-team trade involving the Pirates and Rays.