ST. LOUIS - It took until the 19th inning, but the Mets finally figured out a way to score a run yesterdaySaturday at Busch Stadium: Wait until the Cardinals had to use an outfielder to pitch.

More than six hours after the game began, Jeff Francoeur’s sacrifice fly off Joe Mather — yes, an outfielder by trade — put the Mets on the scoreboard. But unlike everything else about yesterday’sSaturday's game, the celebration didn’t last very long. While the Cardinals had to use position players on the mound, the Mets kept Francisco Rodriguez in reserve — and the $36-million closer couldn’t do his actual job. Yadier Molina’s two-out single in the 19th tied it at 1, but the Mets fought back to win it in the 20th.

Jose Reyes’ sacrifice fly off Mather drove in Angel Pagan, who had led off with a bunt single, and Mike Pelfrey earned the save as the Mets outlasted the Cardinals, 2-1. “I’ve never played 20 innings in my entire life,” said Reyes, who will send either his cleats or bat to the Hall of Fame for scoring one run and driving in the other. “It was a crazy game, a crazy game. We’re happy that we survived all 20 innings.”

The 6-hour, 53-minute contest was the longest game by time for the Mets since 1974, when they went 7:04. It was the longest by innings since 1964, when they went 23 innings in an 8-6 loss to the Giants at Shea Stadium. “It was big for us,” Mets manager Jerry Manuel said. “We needed to win this game. They were fighting all day to stay in the game. Hopefully, that’s a sign of things to come for us.”

Fortunately for the Mets, Cardinals manager Tony La Russa went to Mather, because the Mets couldn’t solve Felipe Lopez — the Cardinals’ third baseman — in the 18th inning. Still, Francoeur said it was no gimme facing Mather in the 19th.

“I thought it was just a matter of time, but I’m not going to lie to you,” said Francoeur, who was 0-for-7 before the sacrifice fly. “It was the most nervous I had been in a long time hitting. If I ground into a double play against the pitcher, you’re never going to hear the end of it.”

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K-Rod couldn’t provide any relief — literally — for his tired teammates, allowing Albert Pujols’ one-out double and Molina’s tying single in the 19th. But he had a legitimate excuse. Rodriguez said he had warmed up more than 10 times since the eighth inning and thrown more than 100 pitches in the bullpen.

“I had a dead arm out there,” he said. “’I didn’t feel good. But the bottom line is that we got the win.”

The Mets didn’t get their first hit until Pagan’s bloop single off starter Jaime Garcia to open the sixth. They didn’t get another one until Luis Castillo’s one-out single in the 12th.

If there were a silver lining to enduring the marathon, it had to be the performance of Johan Santana, who struck out nine and walked one in seven innings.

After Pujols went 0-for-3 against Santana, the Mets pitched around the three-time MVP with their bullpen — and put him on three times to load the bases in the very late innings because the No. 4 hitter, Matt Holliday, had been double-switched out. Afterward, La Russa revealed that Holliday was sick and could not continue.

“We were able to hang around, hang around, hang around,” Manuel said. “Lay on the ropes for about nine innings and then waited for all the other guys to get out of the game.”