BOSTON — Through the doors of the Miami Heat locker room after their stunning Eastern Conference finals upset of the Boston Celtics rang the Slim Thug lyrics, "Who the motherf***ing boss?" His teammates' answer, echoing into the hallways of TD Garden's underbelly: "Jimmy Butler is the motherf***ing boss."

Behind those same doors, a Heat staffer delivered Caleb Martin a Gatorade cup containing their shot of choice. They toasted each other, threw back their makeshift snifters, and Martin washed his down with a sip off a Pacifico, before bopping his head to the music blaring from Udonis Haslem's Bluetooth speaker.

Butler and Martin combined for 54 points in a 103-84 blowout of their hosts in Game 7 on Monday night, clinching a second trip in four years to the NBA Finals, where they will meet the Denver Nuggets. Butler, a six-time All-Star and five-time All-NBA selection, edged Martin, an undrafted free agent who was waived by the Charlotte Hornets 21 months ago, in the Eastern Conference finals MVP award voting by a 5-4 margin.

"I'm just confident," said Butler, who collected 28 points, 7 rebounds, 6 assists and 3 steals in Game 7. "I know the work that we all put into it, so I know what we're capable of. Nobody is satisfied. We haven't done anything. We don't play just to win the Eastern Conference; we play to win the whole thing."

"I definitely reflect on where I started and the journey it's taken to get here," added Martin, who joined the Heat on a two-way deal in September 2021 and signed for the mid-level exception last summer. "But more than anything, it's a weird feeling, because as happy as I am, as grateful I am to be here, I also understand that we have four more. The job is not done. We didn't go through what we went through all season and my personal journey to stop here. We are trying to get what we came here to get, so we've got four more."

Somewhere on the spectrum that spans those players lies the essence of Heat Culture, a once-ridiculed and now undeniable spirit born from a roster full of long shots and castaways who never stop believing. That faith made Miami the second No. 8 seed in league history to reach the Finals and the first to do so both in a non-lockout season and after trailing in the fourth quarter of a second play-in tournament game.

"Life comes at you fast, man," Heat forward Kevin Love, the 34-year-old five-time All-Star who was waived by the Cleveland Cavaliers in February and is now bound for his fifth career appearance in the Finals, told Yahoo Sports. "Sports, like in life, fortune and momentum can change on the drop of a dime, and it's just been a beautiful thing to be a part of this group and a part of this locker room. It's really been special."

One year to the day since the Celtics led Game 7 of the 2022 conference finals wire-to-wire in Miami, the Heat returned the favor, charging to a 22-15 first-quarter advantage, never trailed for the night's final 40 minutes and led by as many 23 points. They shot 50% from 3-point distance (14-of-28) for the third time in the series, matching the number of games they hit that mark over the course of their 44-win regular season.

"What happened last year obviously was on our mind, and it drove us this year," said Heat coach Erik Spoelstra. "That's what you always hope for with competition, that it can drive you to a higher level. I think that's what you saw in this series, this year, to be able to have to overcome a lot of stuff."

History was waiting on the other side of Monday for the Celtics, too, only they left their business unfinished. Boston became the fourth NBA team ever to force a Game 7 after trailing a series 3-0, and the first to host that chance to snap the winless streak for teams in that situation at 0-150. That miracle required another on Saturday, when Derrick White's Game 6-winning tip-in might have broken most teams. But not the Heat.

"It was a devastating loss. Trust me," Haslem, the 42-year-old Heat captain who will make his seventh trip to the Finals in his 20th and final season, told Yahoo Sports of his team's response to Saturday's defeat. "It took us a little while to get our balance, but we had another game. We had another opportunity to come to Boston and play for a Game 7. What better opportunity to win a Game 7 on the road in the Boston Garden."

Celtics star Jayson Tatum turned his ankle on Monday's opening play, a drive past Martin and into Gabe Vincent. He made 1 of the 2 free throws and was never the same in 41 more minutes on the floor.

Neither was Boston.

"I was a shell of myself," said Tatum. "It was tough to move."

"The ankle was really killing him," added Marcus Smart, one of nine Celtics to shoot worse than 50% from the field (4-of-10 FG). "He tried to fight. It just didn't go in his favor. It didn't go in any of our favors."

When Tatum first went to the bench to rest his swelling left ankle for the final 4:11 of the opening quarter, Miami flipped an 11-8 deficit into the 7-point advantage by quarter's end. The rest was a rock fight the Heat won in a knockout. Tatum scored just 14 points on 13 shots. The Celtics turned to Tatum's co-star, Jaylen Brown, whose nightmare performance ended with as many turnovers (8) as made field goals (8-of-23).

"Just a terrible game when my team needed me most," Brown said. "JT hurt his ankle, first play of the game, and you could see it swelling up on him. He couldn't move out there. It was tough for him. My team turned to me to make plays, and I came up short. I failed. It's tough. Credit to Miami, but just a terrible job."

Only White gave the Celtics a reason to believe beyond a first half they were lucky to be trailing only 52-41. His 8 straight points early in the third quarter drew the Celtics within 8. They got no closer than 71-64 inside of a minute left in the third. Two missed calls in the next 50 seconds — Butler stepping out of bounds prior to a Martin 3 and Martin double-dribbling into a jumper — swung the margin back to double digits.

The fourth quarter started worse for Boston. Tatum missed a layup out of the gate, and Martin answered with another 3. Officials waved off Brown's ensuing layup over Bam Adebayo to whistle an offensive foul. Butler responded with an 18-footer. Butler poked loose Brown's seventh turnover and ran out to a dunk for an 83-66 lead. When a Tatum dunk stopped the bleeding several possessions later, he could hardly hobble back on defense. Say goodbye to the Celtics' series comeback and hello to the eighth-seeded Miami come-up.

This was the sport at its most heartbreaking and heartwarming, all at once.

The Celtics finished 9-of-42 from 3-point range (21.4%), spun 15 turnovers into 21 Miami points, missed countless defensive rotations and lazed underneath multiple screens to free scorching Heat shooters. As the final buzzer sounded on garbage times, Boston's Grant Williams entered the tunnel first among his teammates, lamenting out loud, "Not gonna play hard in a Game 7?" White trailed behind him, the Game 6 hero's head hidden beneath a towel, followed by Tatum, limping from one end of the hallway to the other.

In between was the visitors' locker room, where the Heat would soon crack their celebratory beers.

"Tastes great," Love said of that first sip after a Game 7 win. "Never better."