MIAMI — Gabe Vincent drilled another 3-pointer after Marcus Smart missed another layup to give the Heat a 23-point lead early in the third quarter, and Jimmy Butler kneeled at center court, signaling for a Celtics timeout (which rookie coach Joe Mazzulla called for once). It was the same taunt Al Horford tried earlier in the Eastern Conference finals, before Boston blew its first of consecutive 12-point leads to open the series.

At the same time, Miami wing Max Strus drew a technical foul for taunting the Celtics. The same Max Strus who the Celtics waived in order to make Tacko Fall their human victory cigar for 169 garbage-time minutes.

"Jimmy got that one for me," Strus said of the first taunting tech of his NBA career. "I was just piggybacking off of him. Probably not smart, but I'll take it. Whatever." And what did Strus say? "Can't say that in here."

Miami was laughing at heavily favored Boston on its way to a 128-102 win and a stunning 3-0 series lead. Two rounds after eliminating the top-seeded Milwaukee Bucks in five games, the Heat have a chance to sweep the second seed and advance to the NBA Finals at home in Game 4 on Tuesday (8:30 p.m. ET, TNT).

There is no sense in breaking down this game beyond repeating that Miami molly-whopped the Celtics until they quit, if they hadn't already given up before they got on the plane. It was easily the most embarrassing Boston effort in a handful of them this postseason, and Kaseya Center straight-up partied at the funeral.

"It was loud in here, man," said Miami sharpshooter Duncan Robinson.

Not two minutes passed from the Strus tech before Jayson Tatum walked back on defense, allowing Caleb Martin to make another wide-open jump shot. Tatum committed his third turnover on the next possession, leading to a Strus layup. The Heat led, 83-56, Mazzulla called another timeout, and it somehow got worse.

Miami led by as many as 33 points. It might as well have been 69. The game was a joke.

A cast of undrafted Heat — Vincent, Strus, Robinson and Martin — combined for 79 points on 28-of-45 shooting (62.2%), including 17-of-31 from deep (54.8%). The entire seven-man rotation the Celtics used to beat the Atlanta Hawks and Philadelphia 76ers in the first two rounds scored 59 points on 24-of-72 field goals (33.3%) and 6-of-31 accuracy from distance (19.4%). Vincent, who was playing in Sioux Falls when last the Heat beat the Celtics in the conference finals, scored more points (a playoff career-high 29) than All-NBA wings Tatum and Jaylen Brown combined (26 points on 12-for-35 field goals and 1-for-14 3-pointers).

Need we say more? In a game they desperately needed to win, the Celtics responded to losing the opening quarter, 30-22, by letting Robinson waltz through the lane for a layup on the first possession of the second.

Rather than push the pace in transition, Marcus Smart, trailing by 13, figured the only way he could create offense was to flop in the backcourt. He was whistled for an offensive foul instead. Down by 21, Brown and Tatum just stared at each other at the top of the key until Brown launched an errant 3 with nine seconds left on the shot clock. It was unclear if they even had a game plan. If they did, it didn't much matter, because Smart, Tatum, Brown, Horford and Malcolm Brogdon all shot airballs. This is a thing that actually happened.

"Just being transparent, it's unfortunate," said Tatum. "We obviously wanted to come out and perform better, play better, have a different outcome, or at least give ourselves a chance. It's tough. For whatever reason, we didn't have it tonight. At this point of the season, you don't want to say that, but that's on us."

At one point in the second quarter, the Celtics cut the deficit to 15, had a chance to slice it more, and rather than attack, Derrick White slowed enough on the break for Cody Zeller to block his shot. Naturally, on the other end, Butler scored on Grant Williams, drew a foul and lay on the court pointing at the Celtics forward for what seemed like forever, mocking him in front of a national audience for a second time in three days.

Nobody of note even played the fourth quarter. Boston had long since quit.

"I don't even know where to start," said Brown. "It's an obvious letdown. We let our fan base, organization and ourselves down, and it was collective. We can point fingers, but in reality it was just embarrassing."

Never has a coach sounded closer to handing in his resignation while a series is still ongoing than Mazzulla.

"I just didn't have them ready to play," he said. "I should've, uh — whatever it was, whether it was the starting lineup or an adjustment, I have to get them in a better place, ready to play, and that's on me."

Is there a disconnect between the coach and his players?

"Yeah," added Mazzulla, "that's where I have to be better."

Mazzulla can try to absolve his players, but they were every bit as responsible for Sunday's debacle.

Mazzulla acknowledged his team has lost the defensive identity that carried them to last season's NBA Finals and insisted he has to help them discover it again. Tatum echoed that sentiment, saying, "We just have to do a better job of being there for one another, having each other's back and just being a little more connected." What neither of them appeared to realize is just how difficult that is to accomplish in 48 hours.

Conversely, at Miami's podium, Heat coach Erik Spoelstra seemed to be taking pleasure in his team twisting the knife into the same Celtics who sent them home in last year's seven-game conference finals.

"Everything that we went through previously, some of the emotions are coming out," said Spoelstra, a win away from a sixth Finals appearance. "I like that, and we're just going to direct this and keep on focusing at the task at hand. We'll decompress tomorrow, but we'll really get our minds right to finish this thing off."

If Boston cannot do something all 149 teams in its position previously could not — come back from a 3-0 deficit — changes are on the horizon. A sweep at the hands of an eighth seed, no matter how tough Miami is, means the Celtics can no longer convince themselves they have the fight to use this as fuel next season. The coach's job is almost certainly on the line on Tuesday, and the roster might need reworking, too. We will know for sure just how invested the Celtics are in having each other's back if they quit again in Game 4.