ST. LOUIS -- A baseball sat perched atop Oliver Perez's locker in the Mets' clubhouse Sunday night, commemorating his first postseason victory.

What distinguished this ball, given to Perez by reliever Guillermo Mota after recording the final out, was its fairly pristine condition. Most of the others put into play in Game 4 of the National League Championship Series at Busch Stadium were battered and bruised beyond recognition.

Led by Carlos Delgado and Carlos Beltran, the Mets came lashing out of their offensive slumber with four homers in a 12-5 rout of the Cardinals to even the series at two games apiece heading into Monday night's Game 5 -- weather permitting.

"Our team, doesn't matter how far behind we are in the game, we're not going to quit," Beltran said, having homered twice. "We've done it so many times this season, we believe in ourselves."

Perez, a spot starter for the Mets with a spotty history, came to the assignment hoping to keep his team in the game -- and did precisely that.

Working 5 2/3 innings in front of his father and brothers among 46,600 in the stands, the pride of Culiacan, Mexico, was the beneficiary of a Mets eruption that featured five RBIs by Delgado -- a three-run blast in the fifth inning and a two-run double during a six-run sixth that broke the game wide open.

"He did a great job," Game 5 starter Tom Glavine said of Perez, who came to the Mets from Pittsburgh at the trading deadline. "I'm happy for him and proud of him.

"After getting shut out the night before and going a couple of innings without scoring in this game, it certainly was a relief for everybody when we got going."

Constantly in trouble, Perez reached deep and got outs when he needed them, leaving seven runners stranded, while giving up single runs in the second, third and fifth innings. The southpaw kept the Cards in check long enough for the Mets' offense to finally regain its stroke and swagger, starting with solo homers by Beltran and David Wright in the third.

"We've got a cool confidence in us," said Wright, who busted out of an 0-for-13 slumber with his blast against Anthony Reyes for a 2-1 lead just after Beltran's first homer. "There was a sense of urgency, and we got the job done. It was only a matter of time before we'd bust out -- and we busted out tonight. We have confidence in ourselves. We know we can go out and score some runs."

The Mets can take a lead back to New York if Glavine repeats his Game 1 mastery of the Cards in a Game 5 rematch with Jeff Weaver.

Rain, which usually follows the brand of thunder and lightning produced by the Mets' offense, is forecast for Monday.

Glavine, who will be working on short rest if the game goes on as scheduled, coolly noted that "an extra day of rest [with a postponement] is not going to hurt anybody" -- especially a pitcher at the finish of a long season.

The Mets hitters probably would like to come back swinging after setting a collection of club postseason records -- for runs in a game (formerly 11, in the 1969 NLCS against Atlanta), extra-base hits (six), runs in an inning (six, tying a 1999 outburst against Atlanta in the NLCS).

"We were aggressive, but patient and selective," said Jose Valentin, whose three-run double, his second hit of the night, was the final blow of the six-run sixth. "It's nice to see that offensive explosion. When you have a game like that, your confidence is a lot higher the next day."

Perez -- who was 1-3 with a 6.38 ERA in seven starts after coming over from Pittsburgh, where he was 2-10 -- finally weakened in the sixth, departing after solo homers by Jim Edmonds and Yadier Molina. David Eckstein had gone deep in the fifth, the seven homers by the two clubs matching a postseason record accomplished twice previously.

Delgado, whose nine RBIs in the series equal Gary Carter's club postseason record from the '86 World Series, delivered his game-turning three-run shot to left in the fifth against reliever Brad Thompson after an error by second baseman Ronnie Belliard on Paul Lo Duca's sharp grounder was followed by a Beltran single.

"He's been, for a long time, one of the best hitters in the game," Mets manager Willie Randolph said of Delgado. "Part of the strength and beauty of what he does as a hitter is he's a power hitter who will go the other way and take what you give him.

"Very, very rare, very unique, to see a hitter like [Delgado] who can turn on you and pull the ball and then can just stay out there and serve the ball the other way."

Delgado, true to character, preferred to talk in team terms.

"We worked very hard all summer to be where we're at," Delgado said. "I'm enjoying these playoffs; it's a blast. But I guess it's going to be that much sweeter when you win it."

Beltran got the home run party started for New York with one out in the third when he launched a Reyes changeup into the right-field seats, ending a stretch of 14 scoreless innings by the Mets. That homer evened the game at 1, after the Cards strung together three singles for a run in the second.

After Delgado flied to left, Wright unleashed a 404-foot shot into the Mets' bullpen. The Cards got even in their half of the third on Juan Encarnacion's RBI triple.

The two earned runs surrendered by Thompson in the fifth doubled the Cards' total for the bullpen in their first seven postseason games. They'd given up one earned run in 21 1/3 innings before Delgado unloaded.

The Mets used another part of their versatile game in the sixth after Eckstein's homer made it 5-3.

Jose Reyes singled leading off the sixth against Josh Hancock and was running on the pitch when Lo Duca bounced a single through the hole to left, advancing Reyes to third.

After a walk to Beltran loaded the bases, Hancock, a right-hander, was allowed to continue against Delgado -- and the big man bounced one over the wall in left-center for a ground-rule double and two more runs.

Lefty Tyler Johnson was summoned after another walk to Wright loaded the bases, and Shawn Green stroked an RBI single to left center. Valentin followed with a bases-clearing double down the left-field line, the inning finally ending with Edmonds running into the center-field wall to take extra bases away from Reyes, depriving the Mets shortstop of two hits in one inning.

After Beltran homered in the seventh against Braden Looper, it was left to Chad Bradford, Pedro Feliciano and Mota to finish the job -- and for Mota to deliver a very important baseball to Perez.