MIAMI >> Down nine early in the third quarter, down 3-0 in the series, the Boston Celtics knew their season was completely on the brink.

Three minutes later, everything looked different.

Jayson Tatum had 33 points and 11 rebounds, Jaylen Brown added 17 points and the Celtics staved off elimination in the Eastern Conference finals by running away in the second half to beat the Miami Heat 116-99 in Game 4 tonight.

“We were just trying to save our season,” Tatum said.

They most definitely found a way to do that. The two big differences: a 30-point edge for the Celtics on 3-pointers, and an 18-0 run in that three-minute, third-quarter spurt that changed the game and — they hope — might end up changing the series.

“We can’t relax,” Celtics coach Joe Mazzulla said. “We have to keep the same level of intensity, the same mindset, the same focus in the next game.”

Derrick White scored 16 points, Grant Williams had 14, Al Horford added 12 and Marcus Smart scored 11 for the Celtics, who still trail the series 3-1 — but sent it back to Boston for a Game 5 on Thursday.

Jimmy Butler scored 29 for Miami, which was outscored 48-22 in a 14-minute stretch that turned the game — and perhaps the series — completely around. Boston would also have Game 7 on its floor as well if it can keep extending this series.

“Tonight we played with pace, purpose,” Tatum said. “We were getting stops. We were getting out in transition. You see layups and free throws go in, the jump shots start to feel a lot easier.”

Gabe Vincent scored 17 for Miami, Caleb Martin had 16 and Bam Adebayo added 10. The Heat shot 8 for 32 on 3-pointers, while Boston was 18 for 45.

No team in NBA history has ever successfully rallied from a 3-0 deficit in a best-of-seven series; 150 have tried, 150 have failed.

But the Celtics gave themselves hope.

“We don’t really have a choice,” Mazzulla said. “It’s do-or-die. Got to stick together.”

The Heat led by as many as nine points in the opening quarter, kept the lead for the majority of the first half and were up by nine again when Max Strus connected on a 3-pointer early in the third quarter.

That was the moment where Boston’s season was at stake.

And the Celtics responded — most emphatically.

The 18-0 run took Boston from down nine to up nine, a huge turnaround that took 3 minutes, 3 seconds. The Celtics were 6 of 7 from the floor during the run, 4 of 4 from 3-point range, Tatum had nine of the 18 points and just like that the defending East champions — who won three playoff games on Miami’s home floor in last year’s playoffs — were rolling again.

“We always say the last one to get is the hardest one to get,” Adebayo said. “I knew they would be desperate.”

Miami got within four late in the third, only to see another lightning-fast spurt by the Celtics — this time, seven unanswered points in 40 seconds. Boston’s edge was 88-79 going into the fourth, after winning the third quarter 38-23, with 21 of those points coming on 3-pointers.

The Celtics kept the lead the rest of the way.

“They got us tonight,” Heat coach Erik Spoelstra said. “You have to give them credit for that. There’s no doubt about it. There’s no questioning it. We’re not wondering about that. They deserved to win tonight. We have to regroup and get ready for a great opportunity in Boston.”

TIP-INS

Celtics: Tatum’s second 3-pointer of the night was the 220th of his postseason career, passing Paul Pierce for the most in Celtics playoff history. … Boston’s last four-game losing streak was in May 2021, late in the 2020-21 regular season. … Tatum’s jumper with 9:22 left put Boston up seven, stopped a Heat spurt — and was his first fourth-quarter field goal of the series.

Heat: Vincent left early in the fourth quarter after turning his left ankle. … Miami was bidding for its first five-game winning streak of the season — not the postseason, the whole season. Its longest win streak of the regular season was four games, back in December.

HERRO UPDATE

Heat guard Tyler Herro, who broke his right hand in Game 1 of Round 1 at Milwaukee, has his brace off and is resuming workouts. “He is starting the process,” Spoelstra said. “There’s no timetable. But he does have the brace off and he’s able to do ballhandling and some shooting.”

CELEB WATCH

Among the celebrities in the crowd: PGA champion Brooks Koepka (who also was at the Florida Panthers’ win in Game 3 of their Eastern Conference finals series against Carolina tonight), NBA superfan Jimmy Goldstein, former New York Yankees teammates Derek Jeter and Alex Rodriguez, and actor Jeremy Piven.