St. Louis ? Mark Mulder will pitch the third game of the season for the Cardinals today, and it’ll be every bit as big of an occasion as Opening Day.

The 17-game winner, the team’s biggest offseason acquisition, gets to pitch against Philadelphia amid the pomp and circumstance of the home opener.

“It’s going to be fun,” Mulder said. “The place is going to be packed with red and white, and it’s going to be a good time.”

Chris Carpenter, a 15-game winner last year, got the opening-day nod at Houston for the NL champions for a couple of reasons: he missed out on the postseason because of a nerve injury to his right biceps, and the Astros are light on left-handed hitters that could have made Mulder’s job easier. The Phillies, on the other hand, have lefties galore with Bobby Abreu, Jim Thome and Kenny Lofton in the lineup.

“We put a lot of factors together, and there’s a lot of things that go into setting up that first time around,” manager Tony La Russa said. “We try to figure out a way we can get off to our best start, and this is the game that Mark drew.”

Mulder led the major leagues with 17 victories in mid-July last season before going 0-4 with a 7.27 earned-run average in his last seven starts. But La Russa said the left-hander shouldn’t be carrying extra pressure into his first start at Busch Stadium.

“He has the same thing to prove that Carpenter, Jason Marquis and Jeff Suppan have to prove,” La Russa said, “that they can take the ball every fifth day and help us try to win a pennant.”

Statistically, Mulder had a much better spring than usual with a 3-2 record and 4.06 ERA in seven starts counting an outing Sunday in Springfield, Mo. The previous two years he had ERAs of 6.75 and 5.60 with Oakland, then totaled 32 victories, which demonstrates the value of judging spring performances for proven players.

“I feel great going into the season,” Mulder said. “I’ve never had great springs but I’ve felt each one of my starts this year got a little bit better, and I’m confident going out there.”