The Celtics finally ran out of gas in Game 7, but it never should have come to this

The Celtics ran out of gas Monday night at TD Garden.

They had nothing left after turning a 0-3 deficit into a Game 7 at home. Regardless of which Boston sports legends showed up in support, the Celtics had nothing left.

Jayson Tatum sprained his ankle on the Celtics’ first offensive play and was never the same. Jaylen Brown’s promise to improve his ballhandling remained a broken one. He committed a ghastly eight turnovers.

And a team that relied so much on the 3-point shot died on that hill. They were horrible from beyond the arc and without a presence in the paint, the offense completely broke down.

And when the Miami Heat began hitting shots, the game was essentially over. The Heat are headed to Denver. The Celtics are headed fishin’ with a long, painful offseason awaiting after a 103-84 loss.

But the Celtics never should have been here. They dropped the first two games of this series at home because they played lazily and lackadaisically. They weren’t prepared for Miami’s intensity; when they finally gathered their guile and mustered some pride, they turned this into a competitive series.

But this wasn’t enough, pushing an eighth-seed to a seventh game is nothing to be proud of. The season was a failure. The Celtics had every path to the Finals they desired. Milwaukee was eliminated. The 76ers imploded. They only needed to overcome the 44-win Miami Heat.

“We failed because we wanted to win a championship,” Al Horford said.

They couldn’t. The Heat returned the favor, beating the Celtics on their home floor in Game 7. They deserved to win. The Celtics have major questions, especially on their over dedication to the 3-point shot and their defensive slippage.

First-year coach Joe Mazzulla, who may have saved his job with the three victories, flatly said no when asked if the Celtics were too dependent on the 3-point shot. They missed 33 of 42 attempts in Game 7, slumping their heads each time another clanged off the rim. Meanwhile, the Heat countered with made buckets, defensive cohesiveness and played with more passion.

The Celtics looked exhausted. Tatum was never the same after rolling his ankle. Brown showed the world that he needs to improve his fundamentals as the club ponders whether to give him a five-year contract extension.

Mazzulla had no more responses in the end. He got outcoached by Erik Spoelstra when it really counted. The Celtics were too predictable offensively, too soft defensively, and too mentally brittle. They cost themselves a possible championship because of their lackadaisical stretches and porous efforts, and this playoff run, which included a whopping six home losses, shows that.

Grant Williams restrains an irate Joe Mazzulla, who was complaining about a traveling called against Jayson Tatum during the third quarter on Monday's Game 7 loss.Barry Chin/Globe Staff

“It’s one of the best locker rooms I’ve been a part of,” Mazzulla said. “Guys cared. They gave it everything they had. That’s the most important thing to take from this. Obviously, we didn’t achieve our goal; we didn’t win, which was our goal. So, we failed in that regard, but it’s not because the guys didn’t have a sense of togetherness, character, and just who they are as people.”

Yes Joe, the Celtics are great people. They did care, but that has nothing to do with execution and focus. They can come together and sing “We Are The World” in unison before every game, but how does that help improve the defense? How does that make the Celtics more versatile when 3-point shots aren’t falling?

How does this team come out so flat for Game 7? They missed shots, got discouraged, lost their intensity, and then eventually relented. They never got untracked this series, looking shocked that lowly, eighth-seeded Miami decided to even attempt to compete with the mighty Celtics.

“That was, you know, that was terrible,” Horford said. “Losing those first two games at home just puts you in such a hole. It just changes everything. To your point, that’s a really good question because we addressed a lot of those things and right now I don’t have the answer for you. We addressed a lot of them, especially after the Philly series and even the Atlanta series.

“We were like, ‘hey, we have to be better, we have to do these things.’ And it’s something that continues to happen. It’s a pattern that happens with us. We’re going to have to do some soul-searching there because some things have to change in that regard. We had a great opportunity, to your point, and we failed. That definitely has something to do with it.”

Brown, who didn’t want to discuss his long-term future, was understandably crushed. He scored 19 points on 8-for-23 shooting with eight missed 3-pointers and those eight turnovers. He is a franchise cornerstone, but perhaps not the cornerstone, and the organization has to determine whether they want to bring him back long-term and how to maximize his talents playing along with Tatum.

“We failed; I failed; we failed the whole city,” a despondent Brown said. “It’s hard to think about anything else right now. More pain. Coming up short. All in all, I think the year was a great year. Those guys in that locker room through any circumstance stepped up. These guys have been a resilient group and it’s pain that we’re here.”

But we all saw this coming. The Celtics pushed themselves to the limit too many times. They allowed themselves no margin for error. They played a clunker at the worst possible time but it’s hard to believe that the coaching change and drama surrounding it, the need to exert energy to win games they should have won more easily, and the effort required to respond from a 0-3 deficit didn’t affect their performance.

They kept testing their ability to respond from adversity by creating more, and finally paid the price for it.

The Celtics finally ran out of gas in Game 7, but it never should have come to this

Read more about the end of the Celtics’ season