Houston ? Roger Clemens watched Albert Pujols, Scott Rolen and the rest of the St. Louis sluggers dig into the batter’s box and take big whacks at Busch Stadium.

Chances are, Cardinals hitters will be a bit more jumpy when they step to the plate at Minute Maid Park.

Clemens is on the mound today for Game 3 of the NL championship series, and the whole Houston season is riding on his right arm. The Astros trail 2-0, beaten up by a powerful lineup that also includes Larry Walker and Jim Edmonds.

Clemens never has been shy about pitching inside, especially in October. And usually right from the get-go.

In other words: Look out, Cards.

“I always feel, as a pitcher, everybody’s too comfortable,” Clemens said Friday, smiling. “Their job as a hitter is to be comfortable. Your job as a pitcher is you don’t want them to feel comfortable up there.”

Then, his eyes narrowed.

“You’ll notice during the game that if I’m making good pitches and guys are getting their nose out where they might not should be, then you’ll have to adjust,” he said. “Simple as that.”

The Rocket set up the greatest performance of his postseason career — a one-hitter for the Yankees in which he struck out 15 — by buzzing Alex Rodriguez in the first inning against Seattle in the 2000 ALCS.

Last year, in what then appeared to be his farewell appearance, Clemens brushed back Miguel Cabrera in the first inning of Game 4 of the World Series. Never mind that the Florida rookie came back to homer in the same at-bat.

“There’s no question that he’s intense when he’s in the game,” Astros manager Phil Garner said. “But it’s not sort of a YMCA, ‘I’m going to go out, play the game and have fun’ kind of deal. That’s not what we’re talking about.

“This is, ‘I love this game, yes, but we’re going to win or somebody’s going to die,'” he said. “It’s almost that serious, I hate to say it like that.”

After losing games started by unheralded Brandon Backe and Pete Munro, the Astros get their best chance to climb back into the best-of-seven series.

Clemens, a top Cy Young candidate after going 18-4 at age 42, will be followed in the rotation by Roy Oswalt, the NL’s only 20-game winner. Both of them went 2-0 against the Cardinals this season.

“Obviously, having the home-field advantage and now having a 2-0 lead is big when you got to go against Clemens and Oswalt,” Walker said. “We have two very quality pitchers ahead of us.”

Jeff Suppan starts Game 3 for St. Louis, followed by Jason Marquis.

No team in baseball postseason history has recovered from a 3-0 deficit to win a series. Down 2-0, the Astros still are in a precarious position.

A trip to the World Series would give Clemens a chance to pitch against one of the two teams where he spent the most time, the Yankees and Boston.

“I’m smart enough not to look that far ahead,” he said. “But don’t think that every time I turn a corner or pick up a phone or I’m getting messages from those guys up there, friends from New York, friends from Boston, and they’re telling me their dream matchup, which would just be another ulcer for me, probably.”