HOUSTON -- It was the best and the worst of the Astros offense, neatly packaged into one of the greatest games in postseason baseball history.

With three blasts, three Astros Killer B's -- Berkman, Brad and Burke -- saved the team from what could have been a devastating loss that would have shifted the National League Division Series back to Atlanta.

Instead, the Astros are headed back to St. Louis for a National League Championship Series rematch with the Cardinals.

"Coming into the series, everyone was like, 'The Astros offense can't score any runs,' " said Lance Berkman, who sparked Sunday's incredible comeback. "Well, I think we did a great job offensively, probably better than we felt like we were going to do coming in. We just got it done."

Berkman hit an eighth-inning grand slam to give the Astros hope, Brad Ausmus hit a two-out, ninth-inning solo home run to force extra innings, and Chris Burke delivered another solo shot with one out in the bottom of the 18th that capped the longest game in postseason baseball history.

It also capped a surprisingly good NLDS for an Astros offense that was supposed to be the team's weakness. After a regular season in which they ranked 11th of 16 NL teams in runs scored, 12th in total bases and 14th in batting average, the Astros rode the bats to a 3-1 series win over the Braves.

Houston put up 4.28 runs per game during the regular season but averaged 6.25 runs in the series to beat the Braves.

"Nobody thought we would be here," said Mike Lamb, who played in each of the two games at Minute Maid Park. "Everybody's written us off. Our pitching has carried us, no doubt. But in this series we had to score some runs, and we did it."

They barely did it.

Shut down for seven-plus innings by Tim Hudson and the Braves, the Astros trailed, 6-1, going into the bottom of the eighth and had been limited to just five hits. Ausmus got things started when he drew a walk from Hudson, and Eric Bruntlett then chopped an infield hit to knock out Hudson.

On came reliever Kyle Farnsworth, who induced a Craig Biggio fielder's choice but then walked Luke Scott to load the bases for Berkman. On a 2-1 pitch, Berkman turned a blowout into a nailbiter.

"It's definitely a career highlight," he said. "I don't even remember running around the bases."

Berkman's opposite-field grand slam traveled just 335 feet, but it was good enough to reach the Crawford Boxes in left field. It was the first grand slam in Houston postseason history and the fourth of Berkman's career, including regular-season games.

But the Astros still had work to do. The slam made it 6-5, and Farnsworth and the Braves were one out from forcing a Game 5 when Ausmus stepped into the batter's box with two outs in the bottom of the ninth inning.

Ausmus, who hit three home runs in 387 regular-season at-bats, looked at two balls before driving a 404-foot home run that sneaked over the yellow line in left-center field. The homer tied the game at 6 and sent the 43,413 fans into a state of delirium.

"When I started getting to the wall, I could tell," Braves center fielder Andruw Jones said. "I knew it was going to go out."

A foot to the left, and the ball might have struck the fence that encloses the visitor's bullpen, which is in the field of play. Then there was the matter of the ball being deep enough to clear the fence, just to the left of the 404 marker.

"That was probably the biggest one I've had." Ausmus said. "That whole game was unbelievable."

Did it look deep enough from the dugout?

"I was begging like everybody else, like the 43,000 [fans] and the 25 in our dugout," said Biggio, who called Ausmus, "our little unsung hero."

Said Berkman: "It just seems like every year, on teams that win, one guy steps up. This year it was Ausmus, and really he's been swinging the bat well for us through the whole second half of the season. So while it's a little surprising, it's not entirely surprising."

But, again, the Astros had work to do. Both offenses were shut down from the 10th through the 17th innings, with Roger Clemens offering three innings of scoreless relief three days after starting Game 2.

Berkman, replaced by the pinch-runner Burke in the 10th inning, said the offense went "dead."

"Pitching-wise I thought we were OK, but you see the position guys wearing down," Astros general manager Tim Purpura said. "They're swings are getting a little slow and you start to wonder, 'Are we ever going to be able to do anything here?' "

Finally, in the bottom of the 18th inning and five hours and 50 minutes after the longest game in postseason history began, it ended on one swing. Burke connected on a 2-0 pitch from Joey Devine and ended the game.

"Big moments like that always go by too fast," Burke said. "I've been fortunate to have some big hits, but obviously nothing even comes close to this.

"But, you know, today was kind of a microcosm of our season. We started off really slow, made a wild flourish there at the end and came out on top. Hopefully, we can keep that script going and play the Cardinals tough."