The start of the game was delayed 29 minutes, and a light rain persisted throughout the majority of the afternoon.
Walker and Andrew McCutchen each hit one-out doubles to right in the first, giving the Pirates a 1-0 lead. Two batters later, Casey McGehee walked. The only other baserunner Wandy Rodriguez would allow was a leadoff single by Alvarez in the fourth, but he was erased when Yamaico Navarro grounded into a double play.
Wandy Rodriguez had seven strikeouts to give him 31 in his past three outings against Pittsburgh. He retired the final 14 batters he faced. Despite conceding that "he still had plenty of pitches to go," Mills lifted Rodriguez after throwing 94 pitches, citing the hot bats of Tabata and McCutchen that were due up.
"It was the right thing to do to get (Myers)," Mills said. "Weather-wise and mound-wise, it was tough."
Carlos Lee had two hits and scored both Astros runs, and Castro had two hits and an RBI for Houston, which has lost five of seven.
Burnett almost matched Rodriguez. He did not walk a batter and had four strikeouts.
Torched for 12 runs in 2 2-3 innings May 2, Burnett has allowed a total of five runs in his other four starts combined.
Notes: Pittsburgh completed a 5-4 homestand in which it scored 23 runs, an average of 2.6 per game. ... Hanrahan pitched the 10th hours after being reinstated to the active roster before the game. He had missed the previous three games on the bereavement list due to the death of his grandmother. ... The Astros traveled to Philadelphia after the game to begin a two-game series in which RHP Lucas Harrell was scheduled to start Monday's opener. ... Pittsburgh will play its first game in the Miami Marlins' new ballpark Monday.