Jimmy Butler was labelled as "one of a kind" after he led the Miami Heat to a shock win over the Boston Celtics in Game 1 of the Eastern Conference finals.

The eighth-seeded Heat came into the series as big underdogs, while the Celtics were rated as favourites to claim this year’s NBA championship.

But despite facing a 71-59 deficit early in third quarter, Butler helped Miami to an improbable road 123-116 win.

The Heat scored a franchise playoff-record 46 points in the third quarter and outscored Boston 66-50 in the second half. 

Butler had 35 points and also recorded seven assists, six steals and five rebounds. He now has five games with at least 30 points this postseason and his play has filled his teammates with confidence. 

"When Jimmy's playing like that, we feel like we can play with anybody, beat anybody," Heat guard Gabe Vincent said after the game, per ESPN. 

"We got a couple guys in this locker room like that, but Jimmy's one of a kind."

"It's fun [to play with him], he is one of the best players in the world for a reason," added Kyle Lowry. "It's just a joy to watch it.

"For a guy that wants it so bad and works so hard at his craft, it's important to enjoy his success. He gives us all the confidence to be successful and be aggressive and be assertive.

"That's what makes him special, that it's not all about him. He's about our group and our team and everyone else."

For Butler, who is hoping to lead Miami to the NBA Finals for a second time, the trust he is shown by all areas of the franchise is proving key.

He said: "We know that Coach [Erik Spoelstra] puts so much confidence and belief in each and every one of us. Coach Pat [Riley] as well.

"Our circle is small, but the circle got so much love for one another. We pump constant confidence into everybody. 

"I'm playing at an incredible level because they are allowing me to do so. They are not putting a limit on my game. They are trusting me with the ball and on the defensive end. 

"I think that's what any basketball player wants. That's what anybody wants out of life is just to be wanted, be appreciated and just let you go out there and rock.

"I really feel as though with anything in life, if you get the opportunity and you have the belief that my teammates, my coaches, Coach Pat, ownership have in me to kind of lead the charge, along with Bam [Adebayo] right now, anything is possible.

"We go out there and we hoop and we play basketball the right way, knowing that we've always got a chance.

"We don't care if you pick us to win. We never have. We never will."

Adebayo supported Butler with 20 points and eight rebounds, while Lowry, Vincent, Caleb Martin and Max Strus all scored 15 points each.

Jayson Tatum led the Celtics with 30 points but did not take a shot in the fourth quarter and Boston are now 4-4 at home in the playoffs ahead of Game 2 on Friday.

"I don’t know why," said Tatum. "You’ve still got to play the game, you've got to make plays, regardless of whether you’re home or away."

Marcus Smart, who had 13 points and a game-high 11 assists, added: "The only thing we need to adjust to is picking up our physicality and playing some damn defense.

"They didn't change anything from the first half that they weren't doing, they just upped their physicality and that's it. That's the only thing they switched. 

"There's nothing tactical, X's and O's, it's just come out and guard your yard. They scored 46 in that third, and they got going, and they made us pay, and they led into the fourth quarter."