HOUSTON (Ticker) -- Even without one of the "Big Three" on the mound, the Houston Astros once again silenced the potent lineup of the St. Louis Cardinals.

Brandon Backe combined with four relievers on a five-hitter as the Astros took a commanding three games to one lead in the National League Championship Series with a 2-1 victory over the Cardinals.

Morgan Ensberg plated the go-ahead run with a sacrifice fly in the seventh inning for Houston, which is one win away from clinching its first World Series berth with its three aces scheduled to start the next three games.

Andy Pettitte will get the call Monday for Game Five against the Cardinals' Chris Carpenter . Should St. Louis send the series back to Busch Stadium for Games Six and Seven, Houston has 20-game winner Roy Oswalt and seven-time Cy Young Award winner Roger Clemens on the hill.

"For us, it's the best one out of three right now," Astros manager Phil Garner said. "It doesn't get any easier. We're in good position in terms of our pitching, our players and everything, but the job's still got to be done."

The Cardinals, who ranked third in the NL with 805 runs, have managed just 10 runs through the first four games of the series and showed their frustration Sunday as manager Tony La Russa and center fielder Jim Edmonds were both ejected by plate umpire Phil Cuzzi.

"(The Astros) have done some really good things, mixed their pitches and patterns up, but we've had so many weapons," La Russa said. "I think no matter how good you pitch, we've got so many weapons, there's a way for us to break through and we haven't."

Backe, who yielded only one hit in eight scoreless innings in Game Five of the NLCS last year, once again stymied the Cardinals. The righthander allowed one run and two hits with three walks in 5 2/3 innings, striking out seven and throwing 52 of 81 pitches for strikes.

"Today was a lot similar to what happened last year in Game Five for me," Backe said. "Going through the first three innings, not giving up a hit, I was thinking deja vu all over again."

After Albert Pujols ' two-out single in the sixth, Backe gave way to lefthander Mike Gallo , who retired Larry Walker on a groundout to end the inning.

"I have to be honest, when I saw Phil coming out and pointing to the bullpen, I was a little upset," Backe said. "The bullpen has been our backbone on the team, so if I'm going to give it up to anybody, I'd rather give it up to our bullpen than anybody else."

Chad Qualls (1-0) and Dan Wheeler each worked a scoreless inning before Brad Lidge got some help from his defense to work out of a major jam in the ninth to notch his third save of the series.

"It just feels amazing right now, but we know we just have to concentrate on tomorrow," Lidge said. "There are going to be great pitchers going at it tomorrow and we know it's going to be a lot of fun. The way our 'pen is throwing the ball right now, we just have to get after it like we know we can and have been."

With the score tied at 1-1 in the seventh, the Astros took advantage of some shaky play from reliever Jason Marquis to push across the go-ahead run. The righthander, who went 4-0 as a starter vs. Houston this season, issued a leadoff walk to pinch hitter Orlando Palmeiro and committed an error on Craig Biggio 's sacrifice.

Marquis (0-1) walked Lance Berkman to load the bases one out later and, after La Russa was tossed for arguing balls and strikes, Ensberg lifted a fly ball to center field just deep enough for pinch runner Willy Taveras to slide home ahead of center fielder Jim Edmonds ' throw.

St. Louis threatened to send the game into extra innings against Lidge in the ninth. Pujols and Walker opened the frame with consecutive singles to put runners on the corners. Reggie Sanders followed with a slow grounder to third base, but Ensberg was able to throw out Pujols at the plate.

"I could see Pujols running in front of me, so when I got the ball it was kind of an easy decision at that point," Ensberg said. "You just hope that you're not going to hit him."

"I thought the ball was going to die in the grass," Pujols said. "I was told to stay, but I thought I had a chance to make it home. I was thinking he would go to first with the throw."

Walker advanced to third when the Astros left third base uncovered.

"I was walking back to third like we always do," Ensberg said. "Apparently we didn't call timeout, so it was just a great heads-up play by Walker to get to third."

John Mabry then hit a weak ground ball to second baseman Eric Bruntlett , who quickly fired to Adam Everett at second base to get Sanders. The shortstop's relay throw to first baseman Lance Berkman just beat Mabry to end the game.

"Our middle infielders took a couple of steps in," Garner said. "We had been playing just a little deeper right there and they turned an incredible double play to finish the game."

" Eric Bruntlett and Adam Everett , they're as good as it gets with turning it," Ensberg said. "That was just exciting."

Backe only struggled in the fourth, when David Eckstein drew a leadoff walk and Edmonds followed with a double. Pujols lifted a sacrifice fly to right field to give St. Louis a 1-0 edge.

After walking Walker, Backe struck out Sanders and got Mabry on a grounder to prevent any further damage.

The Astros got the run back in the bottom of the frame on Jason Lane 's solo homer off Jeff Suppan .

Making his first appearance since September 25, Suppan surrendered three hits in five innings before Marquis took over in the sixth.

"There's a lot of things that are maddening about this game ... We did so many good things, but it starts with Jeff," said La Russa, who refused to comment on his ejection. "To pitch that well with that extended amount of time between starts, it was really extra special." With a runner on first and two outs in the eighth, Edmonds was ejected after Cuzzi called Wheeler's 3-1 pitch a strike. Pinch hitter John Rodriguez replaced Edmonds and hit a drive that Taveras tracked down on the hill in front of the center field fence.

"I think Willy has shown us that he can play in these big games all along the course of the season," Garner said. "He's come up big for us and he's made a couple of really nice plays on the hill out there. That was not an easy play and he did a terrific job on that."