ST. LOUIS - The St. Louis Cardinals caught a break before the game even began.

Reggie Sanders and Chris Carpenter certainly took advantage of it.

Houston's Andy Pettitte struggled in Game 1 of the NL championship series after being struck on the knee with a liner in batting practice. Sanders - rapidly becoming baseball's newest Mr. October - took Pettitte deep with a two-run homer, while Carpenter grounded the Astros with eight strong innings in a 5-3 victory Wednesday night.

St. Louis will go for a 2-0 lead in the best-of-seven series on Thursday. Roy Oswalt, Houston's 20-game winner, goes against Mark Mulder of the Cardinals.

Oswalt better be careful in batting practice.

While taking a leisurely jog around the bases before the opener, Pettitte was struck on the inside of the right knee with a sharp liner. The Astros insisted the left-hander was fine, but he sure didn't look like a pitcher who was 17-9 with the NL's second-lowest ERA (2.39) during the regular season.

Afterward, Houston came clean.

"It swelled up on him and that was probably a little factor in the game," manager Phil Garner said. "He was trying to pitch through it."

Pettitte finished batting practice, then ducked into the clubhouse for treatment.

"It was a freak accident," he said. "I tried to jump over it, but it hit my knee."

With Pettitte hurting, the Cardinals extended the pattern of home-field dominance that held throughout last year's NLCS against the Astros. The home team won every game, giving St. Louis a seven-game victory and a trip to the World Series.

In the league's first championship rematch since 1992, the Cardinals again got the upper hand on their division rival, a team they finished 11 games ahead of in the NL Central. They have to get by the Astros again for a chance at World Series redemption after their four-game sweep by the Boston Red Sox in 2004.

Sanders is sure doing his part. A flop in five previous postseasons, he resembles Reggie Jackson this time around. The 37-year-old outfielder had a homer and 10 RBIs in a three-game, opening-round sweep of the San Diego Padres, including a record six RBIs in the opener.

"Everything is about timing," Sanders said. "I'm just out there doing my thing."

His 445-foot homer came in the first on a 1-2 fastball pitch that Pettitte left over the plate. Sanders knew it was gone before he dropped his bat, and Houston left fielder Lance Berkman barely moved as the ball soared above his head, just missing the scoreboard.

The crowd serenaded Sanders with chants of "Reggie! Reggie! Reggie!" They kept it up when he made a brilliant catch off a drive by Mike Lamb to end the sixth, slamming into the wall and possibly taking away a homer.

Before this year, Sanders' postseason resume was dismal: 36-for-191 for a .188 average, with five homers and 13 RBIs. He's sure turned it around with the Cardinals, his seventh team in eight years.

"I've never seen anything like it," said reliever Ray King, one of Sanders' teammates.

St. Louis made it 3-0 in the second on Carpenter's squeeze bunt, a familiar offensive weapon for the small-ball Cardinals. In the fifth, RBI singles by David Eckstein and Albert Pujols pushed the lead to 5-0.

That was plenty for Carpenter, who missed last year's NLCS because of a nerve problem in his right biceps. A 21-game winner during the regular season, he had a shutout through 6 2-3 innings and escaped a couple of early jams with help from the Cardinals' stellar defense.

Houston finally broke through on Chris Burke's pinch-hit, two-run homer. But Carpenter allowed just five hits and looked every bit like his team's ace. Sixteen of his outs were recorded on ground balls, the Astros continually pounding his sinker and cut fastball into the dirt.

"I was in command of it all night," Carpenter said.

Jason Isringhausen worked the ninth for the save, allowing an unearned run on a sacrifice fly by Brad Ausmus.

A Game 1 victory is usually a good omen in the NLCS. Twelve straight times, the winner of the opener has gone on to the World Series. The last team that didn't follow that path: the 1991 Atlanta Braves.

"Why play 'em?" Garner quipped. "Hey, it's one loss in a best out of seven."

Burke homered in his second straight at-bat, albeit three days apart. His seventh-inning shot followed an 18th-inning homer Sunday that ended the longest game in postseason history, giving Houston an opening-round victory over Atlanta.

But Burke's homer was about the only highlight for the Astros, who mimicked much of their regular season with an anemic offense. Pettitte couldn't bail them out, staggering through six innings.

After going 13-2 with a 1.69 ERA during the final three months of the regular season, the left-hander gave up eight hits and his most runs since he was tagged for six by Baltimore on June 14. Like Carpenter, Pettitte also missed last year's NLCS while recovering from elbow surgery.

"It's unbelievable," Pettitte said. "I was just terrible."