In a season when their character has been questioned, their manager taunted and their hopes extinguished at several low-water points, the New York Mets completed an improbable and sometimes painful journey to the National League wild-card berth tonight by defeating the Cincinnati Reds, 5-0, in front of 54,621 silenced fans at Cinergy Field.

Mets left-hander Al Leiter responded to one of the biggest assignments of his career with a two-hit shutout that stopped one of the NL's best offenses in its tracks. He allowed just seven balls to leave the infield and the Reds didn't get a runner as far as second base until the ninth inning.

Leiter's 135th pitch of the evening was lined to second baseman Edgardo Alfonzo for the final out, beginning an emotional celebration in the middle of the infield and propelling the Mets into a first-round best-of-five series against the Arizona Diamondbacks beginning Tuesday in Phoenix.

The Mets and Reds were forced into this one-game playoff because both teams finished the scheduled season with 96-66 records. Now, it's the Mets who will keep playing, making their first playoff appearance in 11 years.

"I'm drained," Mets Manager Bobby Valentine said. "I'm excited, I'm elated, I've got a lot of emotions. It's wonderful. If anyone can question what this team can do, I'd like to tell them they're not talking about the right group. They took shots to the head and to the body. They're still standing. We're a little tired, but we'll ride the adrenaline."

In a season when they've alternately looked like a team capable of winning the World Series or one that didn't even deserve to make the playoffs, the Mets were at their best tonight.

Rickey Henderson opened the game with a single and trotted home when Alfonzo followed with a home run. All of a sudden, a roaring, rambunctious crowd went silent, and the Mets never came close to losing control.

"When you have a one-game playoff, there's always the chance you're going to face a guy on top of his game, like Al was tonight," Reds first baseman Sean Casey said.

Alfonzo drove in three runs in all, and Henderson added a bases-empty home run in the fifth inning to lead an offense that collected nine hits and eight walks against four Cincinnati pitchers. The top four hitters in the New York order -- Henderson, Alfonzo, John Olerud and Mike Piazza -- were on base 10 times with six hits and four walks.

Leiter did the rest, saving a season that seemed to be lost after the Mets had dropped eight of nine games and watched a four-game lead turn into a two-game deficit entering the final weekend of the season. But while they were sweeping three games from the Pittsburgh Pirates, the Reds were losing two of three in Milwaukee to force tonight's one-game extension of the regular season.

"It's a great feeling," Leiter said. "I really wanted to finish and be out there on the field for the celebration. It was great and hopefully we'll experience it one, two or three more times.

"The early runs made all the difference. I think they were a little anxious. Greg Vaughn swung at a high curveball one time. Sean Casey swung at a couple of pitches he normally wouldn't swing at.

"We got it done. We always believed this is the type of team we'd be."

Once the Mets forced the one-game playoff, they seemed almost relaxed about getting a final shot, thus writing another unexpected chapter to a strange season. They sported a losing record for the first three months of the season. General Manager Steve Phillips was so frustrated at midseason that he fired three coaches and put Valentine on notice.

As for Valentine, the cocky, talkative veteran manager, he twice announced he should be fired if the Mets failed to make the playoffs. Until tonight, he had managed 1,713 games without getting a team to the playoffs -- the third-longest such tenure in history.

Through it all, they survived, winning 65 of 95 games at one point. Some baseball people called them the best team in the game because of their dazzling infield defense, thunderous bats and top-notch relief pitching.

Now, they will have a chance to prove it, beginning Tuesday, when they'll face Arizona's Randy Johnson.

Compared with everything they had been through, tonight may have seemed easy. Reds starter Steve Parris lasted just 2 2/3 innings, allowing three hits and three runs. He was followed by Denny Neagle, who allowed a run in 2 1/3 innings and Danny Graves, who allowed one run in three innings.

Henderson's home run in the fifth made it 4-0, and with Leiter in control, the game might as well have been over.

"We had a chance," Vaughn said. "That's all you can ask. We just got beat by Al Leiter. He shut us down. We picked a bad day to be shut down. Maybe Al Leiter picked a good day to be on top of his game. We've got nothing to be ashamed of, but it's tough right now."