ST. LOUIS – It took them 168 mostly stress-free games to reach this crucible, this fourth game of the National League Championship Series that will ultimately define who the Mets are and determine where they will spend the next two weeks. The Mets’ season did not perish last night, no matter how bleak this 5-0 Cardinals crushing may have been.

But the expiration date is imminent.

“We’ve been in tougher spots than this,” Willie Randolph insisted a few minutes after Jim Edmonds mercifully chased down Carlos Beltran’s gapper with two outs in the ninth, putting an end to a night that was as forgettable as it was indigestible. “We feel like we’re in pretty good shape, even though we’re down 2-1.”

He’s wrong, of course, and knows it. The Mets spent exactly one day in second place during the regular season. After seizing first for good three games deep, there was exactly one day the rest of the way when anyone else in the NL East crept within one game of them. Whatever pressures they’ve felt before now were either artificial or self-imposed.

The fact is, we have precious little anecdotal evidence to gauge just how well the Mets play with their toes peeking over the edge of the cliff, staring at the abyss. But we’re sure about to find out. As impossible as it may have seemed less than 48 hours ago, when the Mets were 4-0 in the postseason and looking like as sure a bet as the Tigers to dive into the World Series, that’s how difficult it now is to imagine them slithering free from an ever-tightening strait jacket. Or even escaping St. Louis with their season intact.

Forget Steve Trachsel. If it turns out that Trachsel has thrown his last hanging curveball as a Met, then this is the image Mets fans will forever retain of him, coming up micro-small on a night when they so desperately needed him to turn in the kind of professional performance that Jeff Suppan did for the Cardinals. If the bruise on Trachsel’s leg is any indication, we aren’t likely to see him in a meaningful inning again for a long, long time.

The more troubling thing is the way the Mets’ vaunted offense wilted so meekly on the first night of the calendar year when it was absolutely necessary to turn the scoreboard into a pinball machine. Suppan is a fine veteran pitcher, but there is no reasonable way to explain how he paralyzed the Mets’ offense across eight superb innings.

“You tip your cap to a guy sometimes,” said Darren Oliver, the one Met who deserved a similar tribute after turning in six shutout innings and providing the lone sliver of a silver lining, allowing Randolph to keep the five primary members of the bullpen in hibernation for one night. “Suppan’s a good pitcher. Sometimes you run into that.”

They simply can’t run into it again in the next few days, for however long this NLCS lasts. Sometimes, a season can be crystallized so simply, so easily, so succinctly. Tonight, the Mets have to do the one thing they did better this season than they ever have before across 45 seasons of National League baseball.

They have to score in the first inning. They need to get to young Anthony Reyes in a hurry, and they need to put a crooked number on the board, a cushion to make themselves feel better, a lead to make Oliver Perez seem like something less than a sacrificial southpaw – a sense that was underlined as he sat alone at a postgame table wolfing down a heaping bowl of vanilla ice cream, wide-eyed at the media throng descending on the visiting clubhouse.

That, above anything else, was the Mets’ signature formula for success all season. They scored 131 first-inning runs, the most in franchise history. When they were playing at their very best, the Mets seemed to be up 2-0 before you ever settled into your La-Z-Boy, up 3-0 before you ever cracked open your first Coors. All they need is a quick 4-0 lead, and for Perez to pitch the game of his life, and for the bullpen to parlay a night’s rest into four or five shutdown innings, and maybe they can start thinking about actually creeping out of the quicksand.

That, or they’d better pray for rain.