Does Miami Heat’s stunning Game 2 win open path to upset for the ages?

About the time Boston fans began leaving quietly into the night with less than a minute left, the small smile of accomplishment began flickering on Miami Heat players. Tyler Herro, at the free-throw-line, offered a quick grin to Bam Adebayo, who offered one back before finishing their night’s work.

Caleb Martin, as the clock ticked toward zero, smiled at Jaime Jaquez Jr., before walking off the court by the stone faces of Boston Celtic players and the stunned looks of their fans.

What had they done in pulling off a 111-101 win in Game 2 of their playoff series? Was this a one-off kind of wonderful night that reversed a 20-point loss in Game 1 and rewarded their resolve?

Or was it a step toward something more surprising? Erik Spoelstra stood amid his players in the locker room afterward, as shown on TNT, and amid the talk of a “very productive” game and caution to rest up on Thursday planted the seed of something interesting.

“We understand, you know, that this is still a long series,’’ he said.

No one outside the Heat expected a long series. No one really thinks an injured, eighth-seeded Heat can pull off what would be the biggest playoff upset in NBA history by beating top-seeded Boston. It would be the greatest story ever dribbled.

The Heat start a rookie, a 20-year-old, an undrafted veteran who was out of a job when the Heat signed him and two mid-level, first-round picks who have three All-Star appearances combined (all three by Adebayo). Four of Boston’s five starters have played in multiple All-Star games.

You can make a sensible case that Boston is better in every area than the Heat except, strikingly, the coaching. This was another night that told you everything about Spoelstra.

“I’m going to give Coach Spo a lot of credit for giving those guys the confidence that they can win,’’ TNT’s Kenny Smith said.

Start there in explaining Game 2. The young Heat were run off the court from the start of Game 1 and lost by 20 points. So, Spoelstra not only had to emotionally help his players regroup but strategically give them something to believe in.

He did both by insisting they take the 3-point shots Boston was leaving open to them. “Take them and keep taking them,’’ as he said. And as TNT’s Smith said, “What player doesn’t like a coach to have confidence in you and tell you to take shots?”

The Heat shot more 3-pointers (43) than regular field goals (32) in Game 2. Somehow, they didn’t seem forced at all. Seven players made at last one. Every starter scored in double digits, even the 20-year-old, Nikola Jovic, who had 11 points and nine rebounds.

The Heat pitched a perfect game Wednesday in that regard, getting help from everyone, everywhere. Herro ran the offense much of the night had had 24 points and 14 assists. Adebayo hit shot after shot when Boston tried to draw close in the fourth quarter and finished with 21 points and 10 rebounds.

In so doing, Herro and Adebayo answered some nagging questions about their games. Next question: Can they do that again? And again?

Boston has the health advantage, the 64-win team advantage, the nine-point favorite advantage, the All-Star-talent advantage and. perhaps, the motivational advantage of the Heat having stolen their season last year in Game 7.

Or maybe that last one is a Heat an advantage? Has it planted the seed of doubt in Boston’s minds? Or maybe the Celtics are just in their own heads?

Jayson Tatum is Exhibit A. He felt the need to flop in an off-the-ball bump with the Heat’s Duncan Robinson in the third quarter. He got that call, but didn’t a couple of others and soon had lost the composure that defines great players in big games.

Tatum scored 28 points in Game 2. Sidekick Jaylen Brown had 33. But they combined for an insignificant nine points in the fourth quarter. Kristaps Porzingis, their big offseason addition, was 1 of 9 shooting.

A bad night at the office for Boston? Or did the Heat unmask a front-running fraud?

“Especially with that team, it’s never going to go how people expect it to go,’’ Tatum said afterward of the Heat.

Sounds like the scars of last season haven’t healed.

It’s still a long way from being the long series Spoelstra talked to his team about afterward. Game 3 will tell us more.

“You don’t realize the Heat culture they have there,’’ Shaquille O’Neal said on TNT.

Game 2 was a win for Heat culture, a testament to Spoelstra’s ways and the kind of surprise that’s the best part of sports. The question now is whether there’s more coming.