The Pirates have won nine of 15 meetings with the Astros in 2011, but Houston is 5-2 in the past seven meetings between the two ballclubs.
Houston was swept in three games by Milwaukee over the weekend and suffered a 4-0 loss in Sunday's series finale. Wandy Rodriguez gave up three runs in six innings to take the loss, while Jordan Schafer, Brian Bogusevic and Jason Bourgeois provided the hits for the Astros, who swept the Pirates in three games at home and had won four in a row before losing all three matchups with the Brewers.
"I was trying to keep the ball off the plate and use movement out there," said Rodriguez. "It worked sometimes, but when I didn't they hit it."
The Astros will also visit Washington on this road trip and will send Henry Sosa to the mound Monday. Sosa will make his sixth major league start and is 2-2 with a 4.34 ERA in five trips to the mound this season. He has won consecutive trips to the hill and defeated the Pirates with six innings of one-run ball in an 8-2 drubbing on Tuesday. Sosa allowed four runs in each of his first three outings.
The right-hander is 1-1 in two road starts this season.
Pittsburgh will commence a nine-game homestand Monday versus the Astros, Marlins and Cardinals, and failed in its bid for a three-game sweep of the Chicago Cubs with Sunday's 6-3 loss at Wrigley Field.
Charlie Morton allowed four runs -- three earned -- and seven hits in 4 1/3 innings to suffer the loss. He walked five and struck out two batters.
"It's frustrating when you're struggling," said Morton.
James McDonald is 1-3 in his last four decisions and takes the ball for the Pirates tonight. He was beaten at Houston in Wednesday's 2-0 loss from Minute Maid Park and gave up two runs -- one earned -- and seven hits in six innings. He is 8-7 with 4.11 earned run average in 27 starts this season.
McDonald, a right-hander, is 1-1 with a 3.74 ERA in five games (4 starts) lifetime against the Astros.