Rodriguez was the last member of the 2005 World Series Astros team. In return, Houston received minor league pitchers Rudy Owens (Triple-A) and Colton Cain (Class-A) and outfielder Robbie Grossman (Double-A).
Rodriguez has posted a 7-9 record with a 3.79 ERA in 21 starts this season. He had been talked about in trade rumors for a while, but his contract was a holdup for some teams. From the Houston Chronicle:
The Astros owe him approximately $4 million for the rest of this season and $13 million next season. The obstacle to trading him had been in part the $13 million club option for 2014 that becomes a player option if traded, essentially guaranteeing Rodriguez $30 million over the life of the deal on another team.
With the Pirates surprisingly contending for a playoff berth, they were willing to be buyers at the trade deadline. For the Astros, the rebuilding continues.