Carlos Hernandez (left) talks to pitcher Darryl Kile during the fifth inning.(AP)

Piazza, who had zero RBI in the opening round against San Francisco, hit an RBI double in a two-run first inning that sent New York on the way to its fourth straight postseason victory.

"He came out swinging tonight," Mets manager Bobby Valentine said.

Behind Hampton, the Mets extended their postseason scoreless streak to a team-record 26 innings before allowing two unearned runs with two outs in the ninth.

Hampton kept the big guy -- pinch-hitter deluxe Mark McGwire -- on the St. Louis bench and left after the seventh with a 3-0 lead. Relievers John Franco and Armando Benitez finished up.

"There had been some doubts cast over Mike because of a small sample of postseason play, and I think he erased those doubts," Valentine said.

Todd Zeile and Jay Payton homered in the ninth and Edgardo Alfonzo scored a run and drove in another for New York.

And it was a good-luck victory for the wild card Mets -- the last seven teams to win the NLCS opener went on to reach the World Series.

"I liked the way we played, I just didn't like the final score," Cardinals manager Tony La Russa said. "Hampton and the Mets were a little better."

Game 2 will be Thursday night at Busch Stadium with Al Leiter starting for the Mets against rookie Rick Ankiel.

Acquired from Houston last winter to win at crunch time, Hampton delivered. He outpitched former Astros teammate Darryl Kile, blanking St. Louis on six hits and silencing the sellout crowd of 52,255.

Hampton began the evening with a career postseason record of 0-2 and a 5.87 ERA in four starts.

A loser last week in the opening round at San Francisco, prompting some to suggest Leiter should start the opener, Hampton tamed a Cardinals team that averaged eight runs a game in its first-round sweep of the Braves.

Not that St. Louis didn't have its chances. It went 0-for-13 with runners in scoring position, stranding 11.

The Cardinals left the bases loaded in the first when Carlos Hernandez grounded out.

"Everyone wants to score as soon as possible," Hernandez said. "They had a big hit when they had men in scoring position, and that was the ballgame."

Still, St. Louis threatened to tie it in the seventh. Trailing 3-0 with two on and one out, Edgar Renteria sliced a long fly that right fielder Timo Perez ran down on the warning track.

Jim Edmonds followed with a high fly that left fielder Benny Agbayani caught just short of the wall, and Edmonds gave an "aw-shucks" skip as he rounded first base.

"I thought it had a chance of going out," Agbayani said. "The ball kind of died down and tailed back."

Hampton struck out four and walked three. He also got the benefit of a defense that paid extra attention to its positioning, making subtle shifts that paid major dividends.

Meanwhile, not even the presence of a few St. Louis Rams -- the NFL team scoring 43 points per game -- helped boost the Cardinals hitters.

Several of the Mets recently expressed relief that their No. 1 nemesis, the Braves, were out of the playoffs. Secretly, maybe they also knew how well they matched up against St. Louis.

The Mets went 6-3 against the Cardinals this season, mainly because New York's left-handed pitchers could cancel out the Cardinals' lefty hitters. St. Louis was just 17-23 in games started by opposing left-handers.

With nearly every Mets player in the dugout leaning on the top railing, Perez got them off to a fast start. Keeping up his role as late-season sparkplug, he led off the game with a double and took third when Kile bounced a curveball for a wild pitch.

After Alfonzo walked, Piazza grounded a double down the third-base line. It was a good sign for the Mets -- the All-Star catcher began the night as a career .211 postseason hitter. Robin Ventura's sacrifice fly made it 2-0.

"I swung the bat a lot better tonight, only because of my teammates getting on ahead of me, giving me the opportunity to drive in the runs," Piazza said.

"A good start for us, we know it's far from over," he said. "Got to keep the pedal down."

Hampton beat out an infield single in the fifth and later scored on Alfonzo's single.

The Mets tacked on three runs in the ninth off Mike James. Zeile led off with a home run, Agbayani singled and Payton homered over the left-field wall.

Mike Bordick was up next, and James hit him with a pitch. There was no trouble between the teams, though, and Bordick left for X-rays on his right thumb, which were negative.

Those extra runs turned out to be meaningful, too.

In the bottom of the ninth, Kurt Abbott, who replaced Bordick, threw away Renteria's two-out grounder as a run scored. Edmonds then hit a single that skipped past Perez for a two-base error, allowing another run to score.

Notes

• Bob Gibson threw out the first ball to fellow Cardinals Hall of Famer Lou Brock.
• Injured catcher Mike Matheny brought out the St. Louis lineup card.
• Mets reserve Joe McEwing, a popular player before the Cardinals traded him to New York in spring training, got a nice ovation.
• The Mets have sold out the last 33,000 tickets left for the possible three games at Shea Stadium this weekend.