Boston Celtics big-man Al Horford called Jayson Tatum a "special player" after they came back from a 12-point deficit at three-quarter time to defeat the Golden State Warriors 120-108 in Game 1 of the NBA Finals.

The Celtics were on the ropes after the Warriors unleashed a 38-24 third-quarter to seemingly take control of the contest, threatening to run away with things as Stephen Curry had 30 points up to three-quarter time.

But the Warriors had no answer for the barrage from long range that came in the final period, with the Celtics hitting nine-of-12 from deep in the quarter and 21-of-41 for the game as the two sides combined to hit a Finals record 40 three-pointers.

The Celtics ended up shooting 15-of-22 from the field in the fourth, winning the quarter 40-16, despite Tatum not scoring in the final 16 minutes of play. 

Instead, Tatum finished with a career-high 13 assists, and Al Horford – who himself had a career-high six three-pointers with his 26 points – told NBA TV that the league is seeing the evolution of the Celtics star.

"He's letting people know man, Jayson is a special player," he said."Even this year, the growth is unbelievable with him. 

"He's the kind of guy where – tonight he was passing, getting assists, getting other people involved while he struggled a little bit shooting – but he's always going to find a way. He's always going to continue to get better.

"That's who we follow – offensively he gets us going, he defends, and then he has the responsibility to find and make plays for others. His maturation is unbelievable, it's something I'm really proud of, because I've seen him grow."

He added: "When the Celtics trade happened, it was something I was grateful for, and straight away I told Jayson. 

"I said 'hey, I can't wait for us to be in those positions, in Conference Finals, and the NBA Finals' – because I believed that much in the group, and I believed that much in him."

When asked about his new career-high in his post-game media appearance, Tatum said it was something first-year head coach Ime Udoka addressed at the start of their relationship.

"That was kind of his message from day-one, just to challenge me to be the best player I can be, and improve other areas of my game," he said.

"We watched a lot of film throughout the course of the season… obviously playmaking was one [area of focus], drawing a lot of attention, and just to help my team out as much as possible.

"He's done a great job of challenging myself, and the group in that aspect."

Tatum was key in keeping the Celtics offense clicking, but his shot was not falling, finishing three-of-17 from the field. 

When asked how he felt about his inability to put the ball in the basket, Tatum emphasised his team-first mentality.

"Ecstatic – 40 points in the fourth quarter," he said. "[Jaylen Brown], Al, Payton [Pritchard], [Derrick] White, those guys made big shots, and timely shots, as well.

"And we won, right. I had a bad shooting night, but I just tried to impact the game in other ways. 

"We're in the Finals, all I was worried about was trying to get a win, and we did. That's all that matters at this point.

"I don't expect to shoot that bad again, but if it means we keep winning, I'll take it."

The Warriors were aggressive in trying to make sure Tatum had no clean looks, and he said sometimes basketball is a simple game.

"Just reading the play – they do a great job of helping, and things like that," he said.

"It's as simple as – if you draw two, find somebody that's open. That's what I was trying to do."

He added: "This time of the season, you feel great after a win, and you feel terrible when you lose, but you've got to just be able to stay mellow, and stay balanced.

"Especially this early – it's far from over, it's just one game, and we have to be ready to respond.

"They're going to make adjustments... we've got to be prepared."

Game 2 will remain in Golden State, before the series heads to Boston for Game 3 and Game 4.