HOUSTON -- The Houston Astros just about ended the playoff chances of the Cardinals.

Tim Redding combined with three relievers on a three-hitter and Craig Biggio drove in three runs as the Astros beat St. Louis 4-1 Sunday to complete a key three-game sweep.

Houston boosted its lead to two games over the Chicago Cubs and dropped the third-place Cardinals 5 1/2 games back with two weeks left in the regular season. The Astros and Cardinals play three more times in St. Louis next weekend.

"You can't start talking about scenarios," Cardinals catcher Mike Matheny said. "We're not going to give up. The guys in here believe in each other, and that's what's gotten us this far, and it's going to continue to get us through the rest of this season."

It was the first sweep over the Cardinals for the Astros since a three-game series in April 1997.

"These games do end up counting more, because if you win three you're in great shape, and if you lose three you end up being in even more of a mess," Astros third baseman Morgan Ensberg said. "You have to put them away, and we did in this series. It was a great series for us."

St. Louis has lost four straight overall, dropping to just two games over .500 at 76-74.

"Obviously, it's going to be tough," Tino Martinez said. "But we're not out of it yet. We've got ... three more against these guys, so we've just got to stay in striking distance until they have to play us at home, and then maybe we can get back in it."

Houston outscored the Cardinals 20-6 and outhit them 29-13 in the three-game series. The Astros are 10-5 against St. Louis this season.

"We came down here thinking we pretty much had to win two out of three," the Cardinals' Kerry Robinson said. "That's our approach to every series, but it just didn't happen."

Redding (9-14) allowed one run and three hits in six innings. He had been 0-5 in six starts since beating Florida on Aug. 1. The Astros scored an average of 1.6 runs in those losses.

Brad Lidge, Octavio Dotel and Billy Wagner each pitched one hitless inning, with Wagner getting his 43rd save in 46 chances, his 21st in a row.

Dan Haren (3-6) lost his fifth straight decision, allowing four runs and five hits in 3 2-3 innings. He is 0-4 in six starts since defeating Pittsburgh on Aug. 11.

"They did everything better than we did," Cardinals manager Tony La Russa said. "I never thought we'd come in here and lose three, but we've got to find a way to turn the page, and we will."

Lance Berkman tripled to start the second and scored on Richard Hidalgo's sacrifice fly, and Houston made it 2-0 in the third when Redding doubled and scored on Biggio's single.

Scott Rolen grounded into a run-scoring double play in the fourth. Biggio had a two-run single in the bottom half after Brad Ausmus singled and Adam Everett was hit by a pitch.

Noteworthy

Jim Edmonds of the Cardinals is in a 1-for-22 slide. He had been hitless in 18 at-bats before a ninth-inning single Saturday. ... Haren hit Biggio at the start of the game. Biggio has been his 24 times, tying Pittsburgh's Jason Kendall for the major league lead. ... This year's NL Central is the first division race in 20 years that has had three first-place teams in September: Houston, Chicago and St. Louis. In September 1983, Montreal, Pittsburgh and Philadelphia each led the NL East.