HOUSTON -- Chris Carpenter strengthened his Cy Young Award credentials, becoming the first pitcher in either league to win 20 games this season, as St. Louis beat Houston, 4-2, on Saturday night at Minute Maid Park.

As a sellout crowd of 42,817 looked on, Carpenter (20-4) went the distance for a league-leading seventh time while winning his 12th straight decision. He also outlasted seven-time Cy Young Award winner Roger Clemens.

"It's just amazing how he does that," Cardinals manager Tony La Russa said. "Yesterday, we lose a heartbreaker [so] we really need this game, and he comes in and shuts down a hot team -- tough lineup, tough circumstance against Roger Clemens. He's done it so many times this year; it's the [darnedest] thing I've ever seen."

Carpenter gave up two runs on eight hits, walking two and striking out eight. He has won his last 12 decisions and is 12-0 with 1.44 ERA in his last 14 starts with three shutouts and six complete games.

The right-hander's amazing level of pitching is matched only by his relentless consistency. He's had quality starts in 26 of 28 outings, including his last 21 in a row. He's 12-0 against National League Central teams. He's unbeaten on the road. He reached 20 victories in just 28 starts, faster than any Cardinal pitcher since Dizzy Dean in 1934.

"I can't remember a pitcher as long as I've been managing who has been so good every time out," La Russa said. "He just concentrates about as good as he can concentrate."

"It has a lot to do with mental strength," Cardinals pitching coach Dave Duncan said. "He prepares as good as you can prepare. He doesn't let anything distract him, whether it's a bad call by an umpire, a call that he thinks is bad, an error, or whatever else might go on. He stays focused on what he wants to do and doesn't let anything distract him from that purpose."

Carpenter is the first Cardinals 20-game winner since Matt Morris in 2001. The Cardinals have won 24 of the right-hander's 28 starts. He leads the league in wins, innings, complete games and winning percentage. He is the first NL pitcher to win 10 straight road games since Hall of Famer Bob Gibson won 12 in 1970 and the first NL pitcher since Houston's Mike Scott in 1986 to have 20 consecutive quality starts.

Just don't try to tell him he's the Cy Young Award winner.

"I try not to let it enter my mind because, again, we've got a long way to go," Carpenter said. "We've got a month left. I've got to go out and continue to compete for the rest of the month, and our main goal is to give ourselves a chance to be in the playoffs."

La Russa echoed those sentiments.

"I think the healthiest attitude for our club [and] for Chris is to just go out and play the game and let the results fall where they may, and then the other stuff falls into place," La Russa said. "What you saw here is what he's been doing."

With the game tied, 3-3, Mark Grudzielanek's double to center off Russ Springer (4-4) scored Abraham Nunez with two outs in the seventh to give the Cardinals the lead to stay. Yadier Molina added a run-scoring single in the eighth.

Lance Berkman's solo homer to the opposite field leading off the sixth tied the game, 2-2, and took Clemens off the hook for the loss.

Clemens left the game after the fifth inning because of a strained left hamstring trailing Carpenter, 2-1. Clemens gave up two runs on four hits, walking two and striking out two.

"Tip your to hat to Roger Clemens. You could tell he was ouchy there, and we didn't get anything off him," La Russa said.

Carpenter knows Clemens from their days together in the Toronto organization.

"I love competing against a guy like him," Carpenter said. "I know him pretty well and I know the type of person he is, and he is going to give everything he's got. It was a well-played game, and it was fun to have Roger out there."

Said Clemens: "He's come a long way since we were teammates in Toronto. He was a good pitcher then. Obviously, he has far more experience now."

The Cards got on the board in the fourth inning. Albert Pujols led off with a single and moved to second on a groundout. Pujols took third on a wild pitch, barely beating the throw in the process, and after a walk to Larry Walker, came home on So Taguchi's ground ball. Molina's infield hit plated Walker to give Carpenter and the Cardinals a 2-1 lead.

Carpenter had trouble in each of the first two innings.

In the first, Craig Biggio singled with one out. He tried to score on Berkman's two-out double down the right-field line, but was out at the plate, as the Cardinals completed the relay from Walker to Grudzielanek to Molina successfully.

"He has the ability to get out of trouble because he knows when to make a big pitch to get a ground ball for a double play or get that big strikeout with a man on third," Houston catcher Brad Ausmus said of Carpenter. "That's why he's 20-4."

Carpenter didn't get away unscathed in the following inning. Consecutive doubles by Mike Lamb and Luke Scott gave Houston a 1-0 lead. Carpenter gave up one more hit in the inning, but escaped further damage by striking out Clemens and getting Willy Taveras to fly out to center.

"I definitely felt better than I felt the last couple of starts, mechanically," Carpenter said. "I felt like I was getting through the ball a lot better. My sinker was better, my cutter was better and my command was better."

When the game ended, the entire team, led by La Russa and Duncan, congratulated Carpenter.

"Everybody was excited for me," Carpenter said. "Twenty is a big number, but if I start worrying about 20, I've got five starts left. I've got a long way to go."