The Boston Celtics have attempted to pull off one of the most difficult balancing acts in sports in recent seasons – trying to win in the present while setting themselves up for the next decade.

But Thursday night, the focus on the future faded into the background. With a 92-88 victory against the Golden State Warriors in front of a raucous crowd at TD Garden, the Celtics increased their stunning winning streak to 14 games and announced to the league that this year’s team, as constituted, will be a force.

That Boston finds itself in this position is stunning. When Gordon Hayward, the team’s marquee free-agent acquisition, suffered a gruesome dislocated ankle and fractured tibia six minutes into the season at Cleveland, it seemed like the focus was going to shift back to the future for Boston.

And with 21-year-old Jaylen Brown and 19-year-old Jayson Tatum in the starting lineup, plus the possibility of a top-five pick coming in one of the next two drafts, it was a future that still looked plenty bright.

But then, after losing their opening two games and trailing in the second half of their third, the Celtics started winning.

And winning. And winning some more.

Suddenly they found themselves riding the league’s best defense to a 13-game winning streak before welcoming the defending champion Warriors for a nationally televised game Thursday night. Surely a game against the team with arguably the greatest collection of talent in league history finally would produce the end to the unlikeliest of streaks.

Only it didn’t.

At times in both the first and third quarters, it looked as though Golden State might run away with the game, particularly when it took a 17-point lead midway through the third quarter.

But other than for brief portions of the game, it was the Celtics – and not the high-powered Warriors – who dictated the terms of engagement.

With officials allowing them to be physical with their more skilled opponents, the Celtics turned the game into a good old-fashioned street fight. That’s why, despite shooting 32.9 percent overall and 21.9 percent from 3-point range, Boston was able to hang tough against a Golden State team that has the league’s best offense by a significant margin.

“They were just tougher and smarter than we were tonight,” Warriors Coach Steve Kerr said.

Much of that success can be attributed to Brown, who played like a 10-year veteran in leading the Celtics in scoring (22 points) while playing ferocious defense.

The fact he did so after the death of his best friend this week makes his performance all the more admirable.

But Brown wasn’t alone. It takes a team effort to hold Stephen Curry to nine points, Klay Thompson to 13 and the Warriors to 40.2 percent shooting overall and 31.3 percent from 3-point range.

Golden State never looked comfortable aside from Kevin Durant, who had 24 points. But even Durant missed a potential tying basket in the final 15 seconds, and the Warriors spent the final few minutes rushing into one ill-advised shot after another.

But the Warriors were rushing because the Celtics made them. The intensity with which the Celtics played, and the physicality that went with it, had an impact on Golden State as the game wore on, and allowed Boston to put the ball in Kyrie Irving’s hands down the stretch to carry the team home.

And Irving did just that, scoring seven straight points in the final three minutes to keep this entirely unexpected winning streak alive.

Boston now has a victory against the defending champs, a 14-game winning streak and the best record in the NBA – three pretty good reasons to believe Thursday night’s game might have been a preview of the 2018 NBA finals. When asked about it after the game, even Curry couldn’t help but feed into the hype.

“It’s very, very likely, right?” Curry said with a smirk, responding to a question on that very topic. “They’re playing the best right now in the East and obviously they (have to) beat Cleveland, who’s done it three years in a row … so we’ll see.

“But I hear the weather is great here in June.”

Even with Thursday’s result in the books, that kind of conjecture remains premature. For as hard as Boston plays, and as good as its defense is, the offense – ranked 22nd in the NBA – remains a problem.

So too is the continued loss of Hayward. Relying on such young players as Brown and Tatum – as great as they’ve been – in the postseason is always a harrowing experience.

And despite the ups-and-downs Cleveland has gone through this season, Curry was correct to mention that the Celtics still have to get past the Cavaliers, and LeBron James isn’t going to cede his throne without a fight.

But the time for doubting the Celtics is over, as is the time for worrying about Boston’s future.

Thursday night, these young Celtics officially arrived, and they’re here to stay.