PITTSBURGH - The Houston Astros, and yes, the Pittsburgh Pirates, might have anticipated this from Roger Clemens and Andy Pettitte. They probably didn't expect it on the same night from rookies Ezequiel Astacio and Wandy Rodriguez.

Rodriguez took Astacio's spot on Houston's roster minutes after Astacio beat the Pirates in the opening game Tuesday night, then pitched even better than he did as the Astros completed a doubleheader sweep with a 6-4 victory.

Lance Berkman hit a two-run homer in the second game and had four hits in the Astros' first road doubleheader sweep since Aug. 4, 1995 - also in Pittsburgh.

In the opener, Astacio limited Pittsburgh to two runs over six innings for his first major league victory, and Morgan Ensberg and Berkman keyed two early scoring innings in a 9-3 victory.

"Going into a doubleheader in somebody else's ballpark and you've got two kids on the mound, you're always concerned, but they did a marvelous job," manager Phil Garner said.

Houston has won 10 of 14 to get back to a game over .500. The Astros (47-46) are 31-16 since starting the season 15-30.

The Astros, held to five runs and 20 hits during a three-game sweep by St. Louis last weekend, have outscored the Pirates 26-8 in the first three games of a four-game series that likely will played in less than 48 hours. A day game Wednesday following a doubleheader presented a precarious situation for the Astros with two rookie pitchers going.

"They've taken their bumps and bruises at times, but they made some adjustments and came out and pitched well," said Craig Biggio, who had two hits and scored twice in the second game - his 2500th in the majors.

The Pirates have been outscored 56-16 in losing seven of eight and are 1-6 since the All-Star break, and seldom-used players are doing much of the damage.

Just as in the opener, when Houston took a 5-0 lead in the third inning against rookie Ian Snell (0-1), the Astros jumped up early with a four-run third against Mark Redman (4-10), who lost his sixth straight start.

Chris Burke and Humberto Quintero singled ahead of Biggio's walk, loading the bases with one out. Eric Bruntlett, a utility infielder making an infrequent start, cleared the bases with a triple and later scored on Ensberg's sacrifice fly.

Previously, Bruntlett had only two RBIs in 44 games this season. On Monday, Quintero drove in four runs to lead an 11-1 win after previously having only one RBI.

Rodriguez (5-4) made the lead stand up to win his third in four decisions, returning from a short stay in the minors so he could pitch during the All-Star break. He took the roster spot of Astacio, who was sent back to Triple-A Round Rock between games, and gave up three runs, two earned, in six-plus innings.

"When you're in a little bit of a rut, it doesn't matter who's out there," Pittsburgh's Matt Lawton said. "Right now we've got to turn it up. I don't know who's going to do it, but we've got to get it done."

Pirates manager Lloyd McClendon shuffled his lineup to try to generate some offense but Lawton, batting third for the first time this season, went 0-for-6 with three strikeouts and hit into a double play.

"But we have to stay professional with our approach and continue to grind it out and continue to believe in each other," McClendon said. "Nobody's going to feel sorry for us."