SAN DIEGO (AP) -With one swing of Albert Pujols ' bat, a St. Louis Cardinals lineup that looked so sickly in September suddenly got a lot better under the California sun.

San Diego Padres ace Jake Peavy tempted Pujols with one pitch too many and the slugger, who has a shot at a second straight NL MVP award, responded with a two-run homer that launched the Cardinals to a 5-1 victory in the opening game of the division series on Tuesday.

Everything went well for the Cardinals, from the second chance Pujols got when catcher Mike Piazza couldn't catch his foul ball to having ace Chris Carpenter fresh for the playoff opener, the result of manager Tony La Russa 's gamble in keeping him out of Sunday's regular-season finale.

Even though they enjoyed home-field advantage for the first time in the opening round, San Diego still can't beat the Cardinals in October. The three-time NL Central champion Cardinals have won seven straight postseason games against the Padres, including division series sweeps last year and in 1996.

Tuesday's win started with Pujols' impressive drive in the fourth inning that broke a scoreless tie. Pujols connected on Peavy's eighth pitch.

''What an at-bat,'' St. Louis leadoff hitter David Eckstein said. ''Being able to foul off pitches, take some pitches and then do what he did, that ignited the whole club.''

Peavy was hoping for far better results than Game 1 of last year's playoff series, when he lost 8-5 to Carpenter at St. Louis while pitching with two broken ribs. Peavy hurt himself when he jumped on Trevor Hoffman 's head while celebrating the Padres' division title several days earlier.

Pujols, though, reminded Peavy and the Padres just how dangerous of a hitter he is. Peavy left a full-count cut fastball over the plate and Pujols drove it an estimated 422 feet into the Padres' bullpen beyond the fence in left-center.

Center fielder Mike Cameron climbed halfway up the fence in a futile effort at Pujols' 11th career postseason homer, which hushed the sellout crowd of 43,107 at Petco Park. Chris Duncan was aboard on a leadoff single.

On Monday, Peavy and manager Bruce Bochy talked about letting the situation dictate whether they pitched to Pujols, or put him on.

''I don't think about if they're going to pitch to me because I want to be aggressive,'' Pujols said. ''If I start thinking a lot of things like that, that's going to take my aggression away. I just take whatever they give me, you know. And if they give me a good pitch today, I'm going to try to put my best swing and hopefully help my team out to win.''

Peavy knew he had little margin for error.

''It was a cutter that was right down the middle,'' Peavy said. ''Yeah, those go wrong a lot.''

The at-bat was kept alive when Piazza got a late jump on Pujols' foul pop and couldn't catch it at the screen.

Pujols thought the ball was heading for the stands. Piazza couldn't tell if the ball hit the screen on the way down, but added: ''I felt like I should have made the play. I really don't have an excuse. It's just one of those things that when you get a situation like that, we need a break to get an out like that.''

Following Pujols' homer, Jim Edmonds singled, Scott Rolen doubled and Juan Encarnacion hit a sacrifice fly.

Pujols hit a three-run homer off Padres rookie reliever Cla Meredith last Wednesday in a 4-2 win at St. Louis that may have saved the Cardinals' season. St. Louis lost nine of its last 12 regular-season games.

Overall, the two-time NL West champion Padres have lost eight straight postseason games dating to 1998, when they were swept in the World Series by the New York Yankees .

Game 2 is Thursday afternoon, when 43-year-old San Diego native David Wells is scheduled to start for the Padres against Jeff Weaver .

While Peavy struggled - he left to a mixture of boos and light applause in the sixth - Carpenter, the reigning NL Cy Young winner, kept the Padres' suspect offense off-balance with his curveball, limiting San Diego to one run and five hits in 6 1-3 innings. He struck out seven and walked one.

Carpenter was pitching for the first time since losing 7-5 to the Padres at St. Louis a week earlier. La Russa gambled on Sunday and held Carpenter out of the regular-season finale in case the right-hander would have been needed Monday in the makeup of a rainout against the Giants. But that became moot when Atlanta beat Houston, giving the Cards the NL Central title.

''If there's a way of pitching him today, our club plays better when he pitches,'' La Russa said. ''Nobody in the league is better than he is.''

Carpenter made adjustments and got out of jams.

''My stuff was good,'' he said. ''My location was good. And my breaking ball was very good.''

The Padres came into this series more confident and healthier than the Cardinals, who backed into the playoffs after barely avoiding one of the worst September collapses ever.

But, said Padres leadoff hitter Dave Roberts , ''Those guys have a lot of confidence when it comes to the postseason. They've had a lot of success. Today was definitely evidence.''

Down 5-0, San Diego finally broke through against Carpenter in the sixth. Roberts legged out a one-out triple to the left-center gap, his third hit, and scored on Brian Giles ' sacrifice fly.

The Padres had two big scoring chances and came away empty, including loading the bases with one out in the seventh, when they chased Carpenter but couldn't score. Second baseman Ronnie Belliard made a sensational diving stop of Todd Walker 's grounder and threw him out to end the seventh.

Carpenter also got out of a jam in the fourth after allowing two singles opening the inning.

Edmonds hit an RBI single for the Cardinals in the fifth and Yadier Molina 's RBI base hit in the sixth gave St. Louis a 5-0 lead and chased Peavy.

Peavy allowed five runs 11 hits in 5 1-3 innings, struck out two and walked one.

Notes: All the Cardinals regulars except Eckstein had a hit off Peavy. Carpenter had a single, too. ... Ryan Klesko and Chan Ho Park both made San Diego's postseason despite regular-season health issues. Klesko pinch-hit in the ninth and hit a fly ball for the final out. Park pitched the eighth.