CINCINNATI — On only his second swing of the season, Albert Pujols knocked one over the wall. A few innings later, he did it again.

The National League’s MVP each of the last two seasons is off to another invaluable start, this time with Mark McGwire providing the pointers.

Pujols went 4 for 5 and had two of the Cardinals’ team-record four homers on opening day Monday, routing the Cincinnati Reds 11-6 on an unseasonably warm afternoon that belonged to power hitters.

Past and present.

Yadier Molina completed the Cardinals’ first four-homer opener with a grand slam in the ninth. Only two other Cardinals have hit slams in season openers — Scott Rolen and McGwire, who was back in uniform on Monday as St. Louis’ batting coach.

Not that they needed much of Big Mac’s help in this one.

“We had a great spring training with him — his knowledge and the things he talked about with the young guys and myself,” Pujols said. “We don’t want to try to make Mark look good. We’re going to try to do the best we can to help our ballclub win, and that’s what we did. If we’re able to do that, we’ll make everybody look good.”

McGwire returned to baseball as the Cardinals’ batting instructor this season, acknowledging that he used steroids when he broke the home run record in 1998. The crowd of 42,493 — fifth-largest in Great American Ball Park history — had little reaction when he jogged onto the field with the rest of the Cardinals coaches pregame.

It was almost as though the fans didn’t realize he was there.

No way they could ignore Pujols.

He got the loudest boos during pregame introductions, then put on a show.

Aaron Harang (0-1) struck out the first two Cardinals, getting the crowd revved. Up came Pujols, who took two pitches out of the strike zone, fouled one off, then connected on a high fastball. A collective “Oh!” rose from the crowd as the ball took flight toward the Reds’ bullpen area.

“You’ve got that crowd going in the first inning, and you want to make sure you find a way to calm them down,” Pujols said.

He added a two-run shot off Mike Lincoln, a line drive that barely cleared the wall. Pujols also singled twice, tying the club record for most hits on opening day.

“That’s why there’s nobody better playing the game today than him,” manager Tony La Russa said. “He’s an amazing player. He works like a maniac and he’s ready every game.”

Pujols won his third NL MVP award overall after batting .327 with 47 homers despite a chronically sore right elbow last year. He had six bone spurs removed from the elbow in the offseason, and didn’t waste time showing he might be even better now.

“If you make a mistake, he’s right on it,” said Harang, who fell to 1-4 in five opening day starts for Cincinnati. “It makes it tough on a pitcher to get him out. The more careful you try to be, the more likely you are to make a mistake. Guys like him and (Barry) Bonds, you can’t be intimidated. The more you try to nitpick, they flourish on that stuff.”

Colby Rasmus, the Cardinals’ top hitter in spring training, also had a solo homer off Harang and caught Rolen’s fly by the top of the outfield fence in the sixth inning. He added a run-scoring single as the Cardinals pulled away in the ninth.

Molina’s first career grand slam off Nick Masset completed the Cardinals’ opening-day splurge that started with Pujols.

“That’s why he’s the best,” Molina said. “He’s the MVP, man.”

Chris Carpenter (1-0) had only one shaky inning out of his six on a sunny, 78-degree afternoon. Joey Votto and Rolen hit solo homers in the fourth off Carpenter, who gave up only seven homers last season, when he led the NL with a 2.24 ERA.

Carpenter has won his last six starts against the Reds, going 4-0 last year. The last time Carpenter pitched in Cincinnati, he had a career day — at the plate, of all things. He hit a grand slam for his first career homer and drove in six runs — a Cardinals record for a pitcher — during a 13-0 win on Oct. 1.

NOTES: Pujols has 34 career multihomer games. He was the last Cardinals player to hit two homers on opening day, in 2006 at Philadelphia. … Pujols’ 17 homers at Great American are the second-most by a visiting player, trailing Houston’s Lance Berkman (21). … Carpenter complained after the game that the baseballs hadn’t been rubbed up enough, making them slippery. He said he had the same problem in a game last year in Cincinnati. … As planned, the Reds designated INF Aaron Miles and OF Wladimir Balentien for assignment to the minors and added INF Miguel Cairo and OF Laynce Nix to the roster. … Former Bengals TE Ben Utecht got a loud ovation and handshakes from Reds manager Dusty Baker and La Russa after he sang the national anthem. … The press box and other areas of the ballpark were briefly evacuated after the game when mop heads caught fire in a dryer.