MIAMI -- At shootaround Tuesday morning ahead of Game 4 of the Eastern Conference finals, Marcus Smart had a message for the Miami Heat:

"Don't let us get one," Smart said. "Just don't let us get one."

It was quite a statement to make, given that the Celtics entered Game 4 in a 3-0 hole in this best-of-seven series -- a deficit that 150 teams have faced over the course of NBA history and not one of them has successfully recovered from.

But, a few hours later, Smart and the Celtics followed through on their part of the bargain, claiming a 116-99 victory over Miami, sending this series back to Boston for Game 5 on Thursday with the Celtics now three more victories away from history.

"Now we've just got to go win another one," Smart said after finishing with 11 points and six assists in 35 minutes. "That's all that matters. We take it one game at a time. We understand the odds are stacked against us, but we're a team that believes in us no matter what, and we've just got to keep going, and all that matters is the next game."

Boston found itself in a 3-0 hole coming into Game 4 because it repeatedly failed to survive adverse situations. The Celtics collapsed down the stretch in Games 1 and 2, then were blown out of Kaseya Center in Game 3.

Game 4, though, was a totally different story. Boston was down nine late in the first quarter after a Caleb Martin 3-pointer. The Celtics were down nine again after a Max Strus 3-pointer 90 seconds into the second half. And then, after the Celtics missed their first four shots and committed three fouls in the first 2:19 of the fourth quarter, coach Joe Mazzulla called a quick timeout with Boston leading 88-83 and the game teetering on the knife's edge.

But in each of those situations, the Celtics responded. They went on a 17-5 run after the Martin triple to take a lead early in the second quarter. Boston went on an 18-0 run over more than four minutes in the third after the Strus 3-pointer. And, after that Mazzulla timeout early in the fourth, Boston got a Jayson Tatum basket on the play following it -- Tatum's first fourth-quarter field goal of the series -- to kick-start a 12-0 run that put the game away for good.

"I think just that poise, the trust in each other, the connectivity I think just throughout a game regardless of how the game was going, that stuff never waned," Mazzulla said. "Listen, when the stakes are really high and you're trying to achieve what we are trying to achieve, it's easy to lose those things because the guys are playing as hard as they can.

"I just thought regardless of the result, the guys just stuck together."

Part of the reason Boston was able to stick together, according to Jaylen Brown, was from conversations the team had as a group together during the day Monday in the wake of a demoralizing blowout loss in Game 3 to send the Celtics to the verge of elimination.

"Just coming together, talking it out," Brown said. "And like a lot of times when you get to this point down 3-0, you see locker rooms and teams start to go in the other direction. We want to make sure that we stayed together. We wanted to make sure that we looked each other in the eye and came out today and put our best foot forward, and I'm proud of our group for doing that because you see teams with their back against the wall and you see they just collapse.

"You didn't see that tonight. You seen us come together, play defense, make the right plays, and I feel like that shows a lot about our character, especially in a game where everything is on the line and everything has went wrong in the last couple of games.".

It also didn't hurt that the Celtics -- and specifically Tatum -- knocked down some shots. Boston had come into this game shooting 31-for-106 (29.2%) from 3-point range over the first three games, compared with 44-for-92 (47.8%) for Miami.

"I still think we can shoot the ball a lot better," said Brown, who had 16 points despite again struggling from deep, going 1-for-5 from behind the arc. "I think I had some good shots that didn't go in, but tomorrow, next game is a new game. I feel like as we continue to build confidence, if we keep seeing the ball go through the net, I think we're going to feel good about ourselves."

Tatum, meanwhile, went 11-for-15 from the field in the second half, scoring 25 points and committing just one turnover after having eight points and four turnovers in the first half.

Tatum had 14 of Boston's 38 points in the third, helping the Celtics outscore the Heat 38-23 in the frame to flip what had been a six-point halftime deficit into a nine-point lead. He then came back into the game after that early fourth quarter timeout and kick-started a game-deciding Boston run with an elbow jumper.

"They were playing zone, and quite frankly we kind of struggled against the zone the first couple games," Tatum said of Miami's defense at the start of the fourth quarter, when the Heat held the Celtics scoreless for over two minutes with him on the bench. "So, it kind of had us stagnant. So, when I came back in, he just drew up a play to get some movement, finding open space, and then make the right play."

Now, as this series shifts back to Boston, the Celtics have at least taken the first step toward making history.

The next one will require another 48 minutes like this one Thursday in Boston.

"We want to come back to Miami," Brown said.