After nearly six hours of baseball, one dramatic comeback by the New York Mets and nearly another, all anyone could talk about was Mark McGwire's monstrous 502-foot blast in the first inning of the first game.

"I was as astounded as anybody. Wow," New York's Mike Piazza said today after the Mets split a doubleheader with the St. Louis Cardinals, winning the opener, 8-7, and losing the second game, 7-5, to fall a half-game behind Atlanta in the National League East.

"That was pretty cool. Nothing he does surprises me anymore."

McGwire hit two home runs in the opener to become the first player to reach 50 homers in four consecutive seasons before the Mets rallied from five runs to win on Edgardo Alfonzo's RBI single in the ninth inning.

The first game featured six home runs and a pair of late comebacks by the Mets. New York made it interesting in the second game, too, scoring three times in the ninth and bringing the tying run to the plate.

McGwire got the day started by launching a gargantuan blast against Octavio Dotel, hitting his longest homer of the season and leaving a dent about 60 feet high on the scoreboard in right-center.

"That amazed me," McGwire said. "That's as hard as I've hit a ball to the opposite field."

McGwire's 50th homer looked routine compared to his first-inning blast. He led off the seventh with a fly ball that just cleared former teammate Shawon Dunston's glove and the 396-foot sign in left-center.

Dunston retrieved the ball but gave it to a fan, not realizing it was McGwire's 50th.

"It would be nice to have, but Shawon didn't know," McGwire said. "It didn't bother me too much because a young kid has it. I hope he'll cherish it."

The Mets came back from a 6-1 deficit to tie it in the eighth on John Olerud's grand slam and Piazza's 30th homer.

Piazza hit his seventh homer in eight games and tied Bobby Bonilla's club record by driving in a run in nine consecutive games. Piazza set the mark in the second game with a two-run single as a pinch hitter.