Celtics forward Jayson Tatum walks off the floor after a 110-97 win in Game 5 of the Eastern Conference Finals against the Miami Heat on Thursday in Boston. Charles Krupa/Associated Press

BOSTON — They must like the pressure. These Boston Celtics sure don’t seem to respond to much else. They’ve owned home-court advantage through the playoffs, but time and time again they’ve shuffled onto the parquet floor of TD Garden and shrugged, then shrank in the moment. That was most evident during these Eastern Conference Finals, when they lost the first two games at home and eventually stumbled into a 3-0 deficit against the Miami Heat.

They’ve also enjoyed a clear edge over opponents in the talent department, again, most noticeably while facing the eighth-seeded Heat. In contrast to Miami, Boston’s roster offers lineup versatility and defensive depth that’s anchored by two young stars. But remind me again – how many series have these Celtics won in four, even five games? Unlike the dominant Denver Nuggets, who are resting after sweeping the Los Angeles Lakers and waiting for their NBA Finals foe to emerge from the East, Boston has found no such inspiration in efficiency.

Instead, these Celtics get their kicks through chaos. Their confidence blooms only after hope vanishes. If there’s a wall, they’ll willingly pin their backs against it and, only then, devise an exit strategy. When given no choice but to unleash the full breadth of their arsenal for the sake of survival, then Boston will play the kind of game that it did Thursday night, and resemble the championship contender it should’ve been all along.

Facing their second straight elimination game, the Celtics never trailed while blowing away Miami with a 110-97 win. The series, now a more manageable 3-2 deficit for Boston, no longer feels like staring up at the impossible. But maybe a mountain was all the Celtics needed to see. When the worst happens, they’re freed to be themselves.

“For some odd reason, even last year, we always seemed to make it a little bit tougher on ourselves,” all-star wing Jayson Tatum said. “But what I do know is that you can see the true character of a person, of a team when things aren’t going well. And our ability to come together, figure things out when it’s not necessarily looking good for us, it’s unlike any team I’ve been on this year and last year, just the core group of guys being able to respond.”

This habit has a history. During the 2020 bubble, Boston faced the then-defending champion Toronto Raptors in the second round. In the deciding Game 7, the Celtics locked down Toronto defensively and wrestled away the 92-87 win. Then a year ago, Boston met another defending champ in the semifinals. This time, they trailed the Milwaukee Bucks three games to two. In Game 6, on the road no less, Tatum scored 46 points as the Celtics won and moved back home for the series finale. They won that game, too.

And for more recent evidence, look no further than the 3-2 lead the Philadelphia 76ers built in the previous round. Boston survived Game 6, and Tatum once again tapped into his clutch gene, scoring 51 in the deciding game. Now, the Celtics are trying to become the first team in NBA history to win a best-of-seven series after dropping the first three games. Before the game, Coach Joe Mazzulla was asked about the team’s mind-set.

“Win or die,” he said, monotone yet tone deaf.

Jayson Tatum, left, and Celtics Coach Joe Mazzulla talk during Game 5 of the Eastern Conference Finals. The Celtics are trying to rally from a 3-0 deficit to reach the NBA Finals. Michael Dwyer/Associated Press

Possibly Mazzulla, who approaches sessions with reporters like daily dental exams, was being intentionally sardonic. Moments later he shared a story about speaking with three young women with terminal cancer. An experience like that gives you perspective about “what life is really all about,” Mazzulla said.

Though their coach sat stone-faced on the pregame dais, talking about life and death, Boston’s players seemed to take a lighter approach. A potential closeout game on their home floor? Just another obstacle for a group experienced in the art of building anxiety.

“We like stressing you all out,” Celtics forward Grant Williams said, smiling.

The Celtics come across as the kind of guys who arrive at the airport 10 minutes before their flight departs. They probably start their holiday shopping at 11:59 p.m. on December 24. They likely think of deadlines as mere suggestions, all the while whistling as the calamity countdown keeps ticking.

“We don’t stress ourselves out. We trust one another. We challenge one another, so in those moments we challenge one another to be better. But when there’s stress, we still smile,” Williams said. “We still come in with the same joyous mentality we’ve had the entire season. We trust one another. Although it may make people panic, we thrive in chaos, a little bit.”

Showing no signs of stress through Game 6, Boston set the tone on the first play when Marcus Smart, the 2021-22 Defensive Player of the Year, sprawled on the floor to get the steal and possession. Smart’s effort led to a layup for Tatum.

“Smart was just a beast tonight,” all-star forward Jaylen Brown said in praise. “Marcus on both sides of the ball was incredible tonight. It was a great performance from him.”

From that aggressive play, the tension went away. Much like Miami’s chances to close out the series in five games.

Boston’s defense, which forced six turnovers in the opening frame, fueled the scoring, and the Celtics nailed seven triples while shooting 54.2 percent. Their lead expanded all the way to 24 points and, picking a good time to post a season first, four Celtics players scored at least 20 points. (Derrick White scored 24, Smart had 23 and both Tatum and Brown finished with 21.)

Following the embarrassment of Game 3, when not a single player scored more than 14 points, a sweep in Miami seemed realistic. But then, as they tend do, the Celtics felt the panic and finally got comfortable.

“I think part of it was just – being down 3-0, you understand how that’s never been done, all the talk about that. It kind of gave us a sense of just like, you know, everybody is counting us out,” Tatum said. “We started to play a little bit more free, relaxed. Obviously, our defensive intensity, being connected on the defensive end, that showed these last two games, and then offensively I think guys are just relaxed and really just taking it one game at a time, knowing we have this uphill battle to overcome. But I really feel like guys have just taken a deep breath.

“In that locker room after Game 3 was the lowest you can be,” Tatum continued, “and I think everybody just kind of relaxed, honestly.”

The Heat still need just one more game to wrap up the series. By Saturday night, maybe Miami starting point guard Gabe Vincent will return to the lineup after missing Game 5 with an ankle injury. Although the Heat replaced Vincent with a veteran, 37-year-old Kyle Lowry was shaky with the ball as an initiator and a liability as a scoring threat.

Though the Heat will be at home, the pressure has shifted dramatically. Momentum is back on the Celtics’ side. Can they handle it?