Johan Santana arrived at Shea Stadium today, put on his no. 57 New York Mets jersey for the first time and said he anticipated little difficulty in adjusting to pitching before some of baseball’s most demanding fans.

“I think the game is the same,” he said. “I’m not going to let that affect what I do on the field.”

The Mets introduced Santana with a choreographed news conference, one that began with video highlights and Latin music. After an extended period for still and video cameras, and a brief statement by Santana, the Mets turned up the house lights of Shea Stadium’s Diamond Club for questions.

Santana answered many with cliches, speaking how he would take things one day at a time, that success was a team effort and that he will have to make adjustments to pitching in the National League. He understands that Mets’ fans demand a World Series championship — or at least an NL pennant — immediately following last year’s September collapse.

“Of course, it has to be this year and beyond,” he said as his wife and father looked on.

Santana walked in past a gift shop already stocked with replicas of his new jersey in home pinstripes and black, and in children’s sizes.

The Mets general manager, Omar Minaya, introduced Santana, who agreed last Friday to a $137.5 million, six-year contract that allowed his trade from the Minnesota Twins to be finalized the following day. Minaya pronounced it was the start of “a great era of Mets baseball.”

“Welcome to the city of baseball,” Minaya said.

Manager Willie Randolph, having acquired an ace for his staff, looked on from his front-row seat.

“You should be happy, Willie,” Minaya said.

Ten days before the first spring training workout for pitchers and catchers in Port St. Lucie, Fla., Santana’s teammates were excited.

“Somewhat it allows us to officially, kind of completely shut the book on ’07,” the Mets third baseman, David Wright, said yesterday. “It kind of takes away from, I guess, kind of the aura of what happened at the end of last year. We can kind of put that behind us. And when your superstars have a fresh attitude, looking ahead rather than behind, I think that that rubs off on the rest of the team.”

Santana, a two-time AL Cy Young Award winner, was just 15-13 last year and lost seven of his last 11 decisions as his ERA rose from 2.60 to 3.33 ERA, his highest since 2001. He allowed a career-high 33 homers — the most in the AL.

“I don’t know, man. It’s part of the game. You’re going to have slumps, I guess,” he said. “I don’t really have an answer for it.”

His agent, Peter Greenberg, said that the deadline for the Twins to make a trade was mutually agreed to with Minnesota general manager Bill Smith around January 22. The initial deadline was January 28, but the sides agreed to push it back a day because executives of some of the interested teams weren’t available.

Santana had a full-no trade clause, which meant he could control his destination. Greenberg said the Mets were Santana’s first choice but that all three bidders were acceptable.

“I think he would have been perfectly happy if he had went to Yankees. I think he would have been perfectly happy if he had went to the Red Sox,” Greenberg said.