By the end of Game 6 on Thursday night, it was clear that the Boston Celtics simply didn’t have any gas left in the tank. Or maybe they looked like they were running on empty in the third quarter, when they fell behind by as much as 22 points. Or maybe it was really at halftime, when the energy in TD Garden was as deflated as a popped balloon as the Celtics went into the locker room with a 15-point deficit.

It doesn’t really matter what you single out as the moment of exhaustion for the Celtics, who fell to the Golden State Warriors 103 to 90 on Thursday night in Game 6 of the NBA Finals to lose the series 4-2, because besides a good start to the first quarter and a push in the third, the Celtics never really looked right in the biggest game of the season. Now, they’ll have to regroup after watching another team take home basketball’s biggest prize on Boston’s parquet.

Boston’s biggest tell this series has been turnovers and that showed in Game 6 as the Celtics gave the ball away 23 times for 20 points on the night. It was a curse for a team that looked like the better squad at times, but just couldn’t execute consistently the way Golden State did down the stretch.

Speaking after the game, Celtics coach Ime Udoka said the team played probably its worst overall series of the playoffs in the Finals.

“And if we play up to the standard of, you know, the Milwaukee or Miami series, it’s obviously a different ballgame, especially in those Games 4 and 5 when we struggled in the fourth quarter,” he said.

There was plenty else that went wrong on the night, too. Finals MVP Steph Curry finished off a historic championship performance with 34 points. Draymond Green played world class defense and finished with a double-double of 12 points and 12 rebounds. Jayson Tatum struggled, especially down the stretch, and finished with only 13 points after shooting just 6 of 18 from the field.

After the game, the Celtics had the blank stares that typically accompany athletes processing the biggest disappointment of their professional lives on live TV. But there was also a spark of a team that maybe hasn’t thrown its best punch yet.

Even without the championship trophy, this Celtics team made it further than almost any honest person thought they would following a dismal 20-21 start to the season. It’s something Al Horford kept in mind went speaking after the game.

“I’m very proud of our group. I’m very proud of the growth of our group all year,” Horford said. “You know, we went from a below .500 team, average team to putting it together.”

That growth is evident when you step away from the immediate reaction to the loss. Tatum was First Team All-NBA and the Eastern Conference Finals MVP whose performance in this series was the mark of someone whose game is still a work in progress, not a finished product. Marcus Smart was Defensive Player of the Year. Jaylen Brown was an offensive spark throughout the series and continues to push the limits of narratives of how far he can go.

“The future is bright,” Brown said. “I always look at adversity as opportunity to shape an individual. And, you know, for whatever reason, it wasn’t our time. And that means we’ve still got a lot to learn.”

A wise master once said that failure is the greatest teacher. And while the loss no doubt stings, there’s no telling what lessons this will impart to a still-young Jayson Tatum hungry to bounce back from his struggles on the biggest stage and a Boston team that proved it could push past previous boundaries.

Udoka said he told his team after the game that this is just the start.

“You know, we’ve seen what we can achieve, it hurts that we fell short of that,” Udoka said. “But, you know, what I did say was the future is bright and we’re just getting started so let’s all come back better from this experience.”

Still, there’s a big difference between getting schooled and being able to apply those lessons. What the Celtics decide to do with their degree is up to them.