ST. LOUIS (Ticker) -- Roy Oswalt ended the home team's dominance in the National League Championship Series. Brad Lidge continued his over the St. Louis Cardinals.

Oswalt allowed one run in seven strong innings and Lidge struck out three over the final two frames as the Houston Astros evened the NLCS at a game apiece with a 4-1 victory over the St. Louis Cardinals.

The Cardinals may have suffered an even bigger loss when left fielder Reggie Sanders , who hit a two-run homer in the series opener on Wednesday and has driven in 12 runs in the postseason, left the game in the eighth inning after spraining his lower back on Adam Everett 's RBI triple.

The NL Central Division rivals are meeting in the NLCS for the second straight year. St. Louis won in seven games last season, with the home team winning each contest, a trend that continued in Game One as the Cardinals posted a 5-3 triumph.

Oswalt (2-0) put an end to that Thursday, yielding five hits and three walks with six strikeouts.

"(It's) not unusual for Roy to have that kind of game, and of course, this is the big stage," Astros manager Phil Garner said. "You know how much trouble we've had winning ballgames in this ballpark. He stepped up large for us tonight and just took control of the ballgame, just absolutely dominated."

The only pitcher to win 20 games in each of the last two seasons, Oswalt was hurt only by Albert Pujols ' solo homer leading off the sixth inning, which cut St. Louis' deficit to 2-1.

"(Oswalt) goes out there and holds that team to one run, with that lineup, it's pretty impressive," Astros second baseman Craig Biggio said. "I told him after the game that I think it's probably the best game he's thrown all season."

The Cardinals threatened against Oswalt one inning later. Yadier Molina hit a ground-rule double with one out and pinch hitter John Rodriguez drew a walk.

However, Oswalt got David Eckstein to fly out to center field and induced a grounder by Jim Edmonds to end the threat.

"With Edmonds up, Pujols on deck and two men on, you've got to get that out," Oswalt said. "I was able to throw a back-door slider and he went out to get it and rolled over it. I thought it was a key situation of the game."

"We actually had three or four or five chances with some of our best RBI guys (at the plate) and he made pitches," Cardinals manager Tony La Russa said. "We battled and had a lot of at-bats against him. We had our chances, but you have to give him credit."

After the Astros added a pair of insurance runs in the eighth, Lidge took over and continued to frustrate the Cardinals. The hard-throwing righthander tossed a perfect eighth and worked around a one-out single in the ninth for his first save of the playoffs.

"It was great to come in with a three-run lead, as opposed to a one-run lead," Lidge said. "It does change your approach a little bit."

Over the last two years - including the postseason - Lidge has not allowed a run in 27 1/3 innings vs. St. Louis, recording 10 saves and 39 strikeouts.

"He's dominated a few people in the last couple of years," Garner said. "He's been a very good closer. Tonight is typical of what he can do."

"Lidge has been the same all year," St. Louis' Mark Grudzielanek said. "He's going to try to get ahead, so you get a fastball, and his slider is so tough to pick up. "It was just a tough day for us, they threw great."

The hero of Houston's 18-inning marathon win over Atlanta in Game Four of the NL Division Series, Chris Burke hit a one-out triple in the second and scored three batters later on a passed ball by catcher Molina, giving the Astros a 1-0 lead.

A run-scoring groundout by Biggio in the fifth pushed the lead to 2-0 before Houston pulled away against the Cardinals' bullpen in the eighth. Lance Berkman led off the inning with a double off Julian Tavarez and advanced to third on a wild pitch.

Burke, who also homered in Game One, delivered a two-out single to plate Berkman.

"It's been a fun ride. Hopefully, I can keep it going," said Burke, who is 5-for-8 with four RBI in the playoffs. "I'm just trying not to think too much about it. I'm definitely having fun and it's been nice getting some hits and helping the guys out, but we still have a long way to go."

Everett followed with a drive to left field that deflected off the glove of Sanders, who hit the ground hard and had to leave the game. Sanders' status for the remainder of the series is uncertain.

"It's serious," La Russa said. "He has some sore spots all over the body. I don't think he broke anything, but he's bruised quite a bit all over and we'll see how he feels. ... I would say probably 50-50, but that's just a ballpark guess."

St. Louis starter Mark Mulder (1-1) allowed two runs - one earned - eight hits and two walks in seven innings. The lefthander struck out six while falling to 1-2 in five starts against the Astros this year.

"Give Oswalt some credit, he outpitched me," Mulder said. "That's the ballgame right there, he shut down our offense and did a good job."

The series shifts to Houston for Game Three on Saturday. Seven-time Cy Young Award winner Roger Clemens will start for the Astros against Matt Morris .

"We're very happy that we got the split and we're going back home," Biggio said. "We have confidence in our ballpark and our fans."

"We've got our hands full, there's no question about that," Grudzielanek said. "We've got to get ready for Roger on Saturday."