What Joe Mazzulla and the Celtics have done to turn things around is simply remarkable

© Jim Davis/Globe Staff Coach Joe Mazzulla kept the Celtics going in the right direction with the Game 5 victory.

The work Joe Mazzulla has done over the past 72 hours, since his lowest point as Celtics coach, has been nothing short of remarkable.

Whatever it was — the threat of losing his job, or the embarrassment of being unprepared for Game 3 or deciding to completely trust all of his players — something has changed in the locker room and in Mazzulla’s approach.

Responding from their trouncing in Miami that put them down 3-0 was impressive but should have been expected from a team picked to win this series easily. But coming back 48 hours later and imposing their will, maximizing their effort, boosting their defense and resurrecting their 3-point stroke has injected full life back into this bunch.

Thursday’s 110-97 win over the Heat in Game 5 at TD Garden only means the Celtics get another chance to play another game Saturday in Miami. But they will enter perhaps the most difficult game of the season having rediscovered the confidence and fortitude that had been lost.

These Celtics have never made things easy on themselves but losing the first three games of this series was going a bit too far. They have yet to completely dig themselves out. They have two more to win, but what they’ve done is shift the momentum of this series, make the Heat uncomfortable and carry a proven game plan and strategy into winning Game 6.

Mazzulla was asked before the game how he has dealt with the win-or-go-home or maybe the win-or-lose-your-job pressure. And just a few moments after calling his approach to Game 5 “win or die,” he made a stunning revelation that he visited young cancer patients in the past few days to gain perspective on life and faith.

“I met three girls under the age of 21 with terminal cancer, and I thought I was helping them by talking to them, and they were helping me,’' he said. ‘‘So having an understanding about what life is really all about and watching a girl dying and smiling and enjoying her life, that’s what it’s really all about, and having that faith and understanding.

“The other thing is you always hear people give glory to God and say ‘thank you’ when they’re holding a trophy, but you never really hear it in times like this. So for me, it’s an opportunity to just sit right where I’m at and just be faithful. That’s what it’s about.

“It makes you better, regardless. I think it starts with that.”

The usually rigid Mazzulla is learning to appreciate the journey, regardless of how difficult it may be. He has been rightfully criticized for his coaching mistakes in this series, for getting lapped by his counterpart Erik Spoelstra through the first three games.

But that hasn’t been the case in Games 4 and 5. Mazzulla’s has helped rediscover the team’s defensive identity, where their aggression and physicality has dictated the past two games. Miami has committed 31 turnovers in the past two games. The Heat look unsure of themselves after looking so flawless and superior for the first three games.

With the media, Mazzulla hasn’t changed his demeanor during these dark times. He said he remained confident the Celtics could reassert themselves, and their Game 4 response, a 17-point win on the road, was an encouraging sign.

Game 5 proved that his words and his game plans are truly having an impact. A disconnected team is suddenly connecting when it is absolutely necessary. That 26-point Game 3 loss that prompted criticism from the likes of Charles Barkley, Shaquille O’Neal and Magic Johnson would have caused most teams to crack. This team staggered but never surrendered.

“I think just being together in moments of adversity, staying on the same page and sticking with it,” forward Jaylen Brown said. “Doubling down on things that we need to do better, holding each other accountable has been the key. I think once we got ourselves together, we all looked each other in the eyes and said hey, we’re not going out like this.

“One, we represent the organization, but we also represent ourselves and our families, and obviously we haven’t performed the way we felt like we needed to perform. So that Game 4 was the start of the atonement, and now we’ve been able to pick up off that in Game 5, and hopefully we can carry it on to Game 6.”

It’s now officially a series. No team has ever come back from 3-0. 13 have come back from 3-1 and 55 have rallied from 3-2. The Celtics have moved themselves into the latter category. The past two games no longer matter. The Celtics have to win two in a row. They’re halfway to the Finals, and the journey is far from over, but it’s definitely attainable.

“One of our assistants put it in great perspective,” Mazzulla said. “The seasons are like nine months long, and we just had a bad week. Sometimes you have a bad week at work. We obviously didn’t pick the best time to have a bad week, but we did, and we’re sticking together and fighting like hell to keep it alive, and the guys are really coming together.

“I think your backs are against the wall, you don’t have a choice. It builds a connection, and it builds just an opportunity. And so like I’ve said all year, the guys in that locker room, they always stick together, and when our backs are against the wall, we just have to continue it.”

Correction: Because of a reporter’s error, a quote attributed to Celtics coach Joe Mazzulla was incorrect in earlier versions of this story. Regarding his approach to Game 5 of the Eastern Conference Finals, Mazzulla said “win or die.”