HOUSTON (Ticker) -- Albert Pujols and the St. Louis Cardinals figured out Brad Lidge just in time.

Pujols hit a go-ahead three-run homer off Lidge with two outs in the top of the ninth inning as the Cardinals stayed alive in the National League Championship Series with an improbable 5-4 victory over the Houston Astros .

One out away from elimination, the Cardinals staged a season-saving rally against Lidge, avoided their first four-game slide of the season and headed home with sudden life in the best-of-seven series, trailing three games to two.

"I'm sitting there thinking, 'They've got the best closer in the game on the mound, but we also have the best hitter in the game at the plate,'" St. Louis starter Chris Carpenter said. "It was an unbelievable feeling. As soon as he hit it, you knew it was gone."

"For the kind of club we have, for the kind of year we had, losing four in a row would have been tough to take," Cardinals manager Tony La Russa said. "We're a better club than that."

Lance Berkman gave the Astros a 4-2 lead with a three-run blast off Carpenter in the seventh.

"The emotions went from high to low and it wasn't much fun," Berkman said. "Right now, this is devastating. I mean we were going to the World Series. We were there, it just didn't happen."

After Mike Gallo and Dan Wheeler combined to pitch a perfect eighth, Houston manager Phil Garner handed the ball to Lidge, who had saved the last three games and has dominated St. Louis over the last two seasons.

"You always know how great these guys are, but they're human," La Russa said. "We had the right part of the lineup coming up. We knew if we could get something going, we'd have a chance."

Lidge struck out the first two batters of the ninth before David Eckstein grounded 1-2 pitch into left field for a single. Jim Edmonds followed with a walk to set the stage for Pujols, who had wasted a pair of RBI chances in the first and third.

"For him to not come through in those situations ... I knew by him not driving anybody in (in his first two at-bats), that he was going to have a great at-bat," Eckstein said.

The reigning NLCS MVP hammered an 0-1 slider off the window facing above the high wall behind the left field seats, bringing a funereal hush over the crowd at Minute Maid Park.

"Basically, he's one of the best closers out there," Pujols said. "I was just looking for a pitch to hit. ... I just couldn't believe that I did it."

"He is a great hitter and he hit a pitch that obviously I would like to have back," said Lidge, who was attempting to become just the second pitcher to notch four saves in a single LCS. "I threw a slider and he hit it a mile."

Entering the series, Lidge had allowed just four hits in 25 1/3 innings over the last two years against the Cardinals, striking out 36. St. Louis did show signs of breaking through against the hard-throwing righthander when it scored a run in the ninth of Houston' 4-3 win in Game Three.

"We did a good job of making sure he has come into the game pretty much every single game," Eckstein said. "When you do that in these type of series when it's back-to-back days and you keep seeing the guy at the end of the game, it just helps your club out."

Jason Isringhausen (1-0) retired all six batters he faced for the victory.

The series shifts back to Busch Stadium for Game Six on Wednesday. Roy Oswalt will try to clinch the series for Houston against Mark Mulder of St. Louis in a rematch of Game Two. Seven-time Cy Young Award winner Roger Clemens would start the deciding seventh game for the Astros.

"This was a tough loss, no question," said Garner, whose team was 78-1 during the regular season when leading after eight innings. "But we've still got a lot of baseball to play. No question in my mind that we'll bounce back and play well."

In last year's NLCS, the Cardinals rallied from a three games to two deficit against the Astros by winning a pair of games at home.

"You're going to have to face two of the best guys in the game," Pujols said. "We were in this situation last year, going to our place, we just have to do it again."

Houston faced a 2-1 deficit entering the seventh when long-time Astro Craig Biggio reached on third baseman Hector Luna 's fielding error. Rookie Chris Burke followed with a hit-and-run single to right field off Carpenter, putting runners on the corners.

Berkman, who hit a clutch grand slam in Houston's NL Division Series-clinching win over Atlanta, sent Carpenter's next offering into the inviting "Crawford Boxes" in left field to put the Astros ahead.

Houston starter Andy Pettitte opened the game by hitting Eckstein with a pitch and walking Edmonds. The Cardinals failed to take advantage as Pettitte retired Pujols, Reggie Sanders and Larry Walker to end the threat.

"You're thinking this doesn't look good for the visiting team," La Russa said. "Those were crooked numbers waiting to happen with Albert, with Larry and Reggie."

Pettitte nearly escaped a similar jam two innings later. Eckstein and Edmonds hit consecutive singles to put runners on the corners before Pettitte struck out Pujols and Sanders.

However, Walker drew a walk to load the bases and Mark Grudzielanek followed with a bloop single to right-center field, plating Eckstein and Edmonds for a 2-1 lead.

Pettitte, who lost Game One, allowed two runs and seven hits in 6 1/3 innings. Carpenter yielded four runs - three earned - and nine hits in seven frames.