BOSTON -- When it was over -- when the Boston Celtics' 18th championship had become an official part of NBA history and the clock had ticked down to 0.0 -- the Boston Garden let out a noise equal parts relief and joy. It went on and on, fans screaming and swearing and belting and cheering, as green-and-white confetti filled the place and the smell of cigars, and something stronger, wafted down.

The Celtics players hugged each other, and met on that storied floor, and cried, as a stage to celebrate them was built among the revelry. The 106-88 beatdown they'd just put on the Dallas Mavericks in Game 5 of the NBA Finals had slipped behind them. Their dominating run through the NBA playoffs was complete.

And the future?

That, at least for the rest of the league watching at home, might have been the scariest thing of all.

Because this may be just the beginning for Boston.

There will be much to unpack about this series in the days ahead: What Luka Doncic must do now, and the lessons he will have to learn from this overwhelming loss, to feel someday what those Celtics players were feeling. Where, exactly, Kyrie Irving had been for much of this series, and certainly on Monday night, when he went just 5-of-16, and 3-of-9 from three, for 15 mostly invisible points.

But that's the past, even the recent past. It's the Celtics' future that could end up being the most important thing about this Boston team.

The NBA is a league made of runs and dynasties, even if this Boston team is the sixth different champion in the past six seasons. But before that, and stretching back through NBA history, are a cluster of teams that won multiple titles: That Boston could join that pattern along with the Golden State Warriors, the Miami Heat, the San Antonio Spurs, the Los Angeles Lakers, the Chicago Bulls -- on and on it goes -- seems very, very plausible.

Yes, the NBA's current collective bargaining agreement is designed to limit superteams, and the prospect of Boston soon entering the second apron, and having to navigate its resulting myriad restrictions, is a hard fact.

But so is just how complete this team already looks to be in the years ahead.

Jaylen Brown, newly minted NBA Finals MVP, is under contract for the long term. Jayson Tatum almost certainly will be before his player option rolls around in two years. Jrue Holiday is under contract for the foreseeable future. So is Kristaps Porzingis. The rest of this core is tied down for at least another season.

And the ins and outs of the CBA that will limit the Celtics' flexibility, especially once Tatum gets his extension, will also pose challenges to the teams chasing them. But Boston has already shown they've crafted at a championship level. Brown and Tatum work. They now know, if they choose, what they'll be spending money on, and how little they'll need to supplement to keep winning.

The fact they play in the Eastern Conference, which appears to be much easier to navigate in the years ahead than the daunting Western Conference, helps, too.

But maybe the starkest indicator of this team's potential burgeoning dominance is how great they were this year -- and how much better they could have been in this Finals.

They went 16-3 in these playoffs, capping off a superb run after boasting the third-best regular season NET rating in NBA history. But while the team's defense dominated -- they held the Mavs below 100 points in all four wins in this series -- the offense that was the league's best in the regular season was in the Finals … fine.

This Celtics team that averaged more than 120 points per game in the regular season, and 111 points per game in the playoffs before the Finals, averaged just under 101 points per game in this series against the Mavs.

Dallas' defense has been good since early March. But not that good.

That Boston could win this thing in five games, without tapping into the best part of its arsenal, should frighten every other NBA team.

Connected to this was Tatum's shooting woes. He, like his team, has a much higher offensive ceiling than he showed en route to his first ring. It's very possible winning an NBA championship will unlock that  part of his game in the years ahead, and perhaps free him, and his team, to play looser going forward.

His 31 points Monday night, and the aggression he showed attacking the rim throughout the night, might signal that fact.

There's also the curious case of Joe Mazzulla, who's rapid rise from the back of the bench two years ago as an assistant coach to NBA championship head coach as of Monday night may also just be the beginning. 

Derrick White called him "a basketball genius" last week. So did the Celtics owner during the festivities here after they'd won. They both may be right. The Celtics coach is a unique guy, but there's a manic intensity and how-did-he-do-that basketball recall that summons up visions of a young Erik Spoelstra.

And at just 35 years old, Mazzulla, also like this Celtics team, may be just discovering what he can accomplish. 

Brown is 27. Tatum is 26. Mazzulla is just starting out his head-coaching journey. Brad Stevens, who put this group together, looks a lot like the most formidable NBA executive in the game. Boston won with Porzingis, arguably the team's third-best player, missing almost the entire playoffs -- he played just three Finals games, never topping 23 minutes played in a single game.

And for the Celtics fans who were still partying throughout Beantown long after the game was over waits this hopeful truth once they wake Tuesday morning, many surely with the hangovers of champions: The fact, as the greats will tell you, that it's the first title that teaches you many of the lessons you need to know in order to win those that follow.

The Celtics have now learned that lesson. And the future, like the present, could belong to them.

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