The Heat’s off, at least for one night, as Boston batters Miami in opener

Well, Miami wasn’t built in a day.

The Heat, the most notorious team in NBA history — before ever taking the floor — debuted its Big Three on Tuesday night, showing that reports of its greatness are exaggerated or, at least, premature.

Smacked across the face by the bigger, deeper and way-tired-of-hearing-about-them Celtics, the Heat did get back in it, cutting a 19-point deficit to three at the end with LeBron James scoring 21 of his 31 points in the second half.

The Celtics then secured their 88-80 win and there went Miami’s perfect season.

“It’s one of 82,” said Dwyane Wade, who went down the chute with Chris Bosh, with whom he combined for 21 points, missing 20 of 27 shots.

“I’m not sure anyone thought we’d go 82-0. It’s not going to happen.”

In a rare triumph of perspective, no one did say anything about a perfect season.

On the other hand, credible basketball people like Jeff Van Gundy said the Heat might break the Bulls’ 72-10 record.

Credible or not, ESPN plans daily updates of the Heat’s chance to win 73, which remains within reach, mathematically.

Unfortunately for the Heat, it had a ragged preseason with Wade missing almost all of it and Mike Miller breaking a wrist at the end, putting him out until the All-Star break.

Nor was it good fortune to open here with proud Celtics, Up to Here with Heat hype.

“Who cares?” said Kevin Garnett, asked once too often about Miami’s retooling. “We did some retooling ourselves.”

Even Coach Doc Rivers, whose manners are impeccable, mocked James’ announcement on his ESPN special.

“Once LeBron took his talents to South Beach, I think everyone got excited,” Rivers said two days before the game.

“Listen, they formed a super team in a lot of ways. . . . Let’s be honest, everybody’s excited about it. Our guys try to downplay it, until you walk in the locker room and hear them talking about it. The [DVD player] is going on all day, watching Miami.”

Since this really was one of 82, and, Miami Coach Eric Spoelstra said, it was also Wade’s first real action since last May, it might be a tad early to write the Heat off.

However, if it was clear on paper Miami was smaller than the top teams, the difference between them and the once-squatty, now-hulking Celtics was scary with Shaquille O’Neal and Jermaine O’Neal alongside Garnett and Glen Davis, even with Kendrick Perkins out.

The slender Bosh looked like a small forward next to them. He played like one, too, taking mid-range jumpers, missing most of them.

So, if Miami will surely be better, watch what happens against the Celtics, Lakers and Magic, who tower over them.

There is also a question of how James and Wade fit. Both have always had the ball; now one must play off it.

James could go into the post, which Rivers called “the scariest change for all of us. . . .

“We’ve been waiting,” Rivers said before the game. “We know it was going to come at some point. And it looks like he’s decided he’s going to become more of a post player.

“I’ve always thought, for him — I don’t know what you do down there [to guard him]. He’s big.”

What you do is pray James doesn’t go down there, as he never seems to.

It only happened a few times Tuesday but stay tuned.

“I think right now it’s a feel-out process for me, D-Wade, for Chris and for the rest of the guys,” James said.

“I talked to those guys. It almost felt like we were being too unselfish. . . . The reason we’re here and the reason we’ve been successful is because we put ourselves to be aggressive at all times, no matter who’s out on the court.

“I think in the third quarter, D-Wade started to be more aggressive. I started to be more aggressive. Even Chris started to be more aggressive.”

Even Chris?

“I know there’s a lot of expectations and a lot of pressure out there,” Spoelstra said afterward, positively, “but we have our own timetable and we knew this wasn’t going to be easy. . . .

“It’s not a reason to panic right now.”

Next week remains a possibility, though.

mark.heisler@latimes.com