BOSTON -- Out of the 160 playoff games LeBron James has already logged in his 12-year career, one in particular just might be the most important of them all: Game 6 of the 2012 Eastern Conference finals in Boston.

The Miami Heat were coming off a Finals meltdown against the Dallas Mavericks in the Big Three's first season together, and found themselves on the brink of imploding all over again, trailing the Celtics 3-2 after starting the series up 2-0.

James was very good in those three losses -- averaging 31.0 points on 51.3 percent shooting, 9.0 rebounds and 3.3 assists -- but he wasn’t great.

What came next in Game 6 was perhaps the greatest postseason performance of his life, considering what was at stake.

James came into TD Garden and put up 45 points on 19-for-26 shooting along with 15 rebounds and five assists. The Heat won by 19, went on to win the series in Game 7 and finished off their season by beating the Oklahoma City Thunder in the Finals, securing James his first of back-to-back NBA championships.

If the Heat lose that game on June 7, 2012, who knows what could have happened. All sorts of scenarios were being discussed in the media from Erik Spoelstra losing his job, to Chris Bosh being traded to even James being dealt for Dwight Howard, who wanted out of Orlando at the time.

But they won, almost single-handedly, because of James and the rest is history.

“It was a defining moment, not only for myself but for our franchise and my teammates,” James said following shootaround Thursday as he was prepping to play his first playoff game back in Boston since 2012, only this time as a member of the Cleveland Cavaliers. “We were counted out by mostly everyone, and for us to come in with the performance that we had, it allowed us to go on throughout that season.”

Where does James personally rank it among his career achievements?

“I’ve got a couple of them, but that’s definitely one that’s up there, just knowing the circumstances and the previous year losing the Finals and having the motivation to get back and redeem ourselves, and being put in a position where not only the franchise at the time, but myself hadn’t been so successful in my career, and to be able to come here in a win-or-die situation and get that victory was pretty huge,” he said.

Before that game, unfair or not, James was criticized for freezing in, rather than seizing, big moments. Since then, he has picked up two Finals MVPs and is continuing to solidify his place in postseason history through the Cavs’ 2-0 first-round lead, passing Michael Jordan for No. 9 in all-time playoff assists in Game 1 and leapfrogging Jerry West for No. 7 in all-time playoff scoring in Game 2.

Did something change for him in that Game 6 in Boston back in 2012?

“Nothing changed, it was one of those types of performances where everything that I had built up to that point, the workouts, the training, the mental preparation, it just leads to that,” James said. “It wasn’t something that was built up in me, it was just something that I had just worked on every single day both mentally and physically, and I was able to come through for my teammates.”

His current teammates remember James’ performance with reverence.

“I definitely remember,” Kyrie Irving said Thursday. “I definitely remember watching it. It was an incredible performance. What’d he have? Forty-seven and 15 or something? Crazy. I was probably watching highlights the last two years of [that game]. But it’s just impressive. That look in his eye, that killer mindset is what we need him to have.”

“Pretty remarkable what he did, down 3-2, coming in and throwing up those sort of numbers it’s just sort of crazy to see that,” added Kevin Love, who, like Irving, said he has seen the game replayed on NBA TV’s “Hardwood Classics” series. “He put the team on his back and he carried them to victory.

“When he gets that look in his eye and he’s determined, naturally you don’t want to go against him, you want to be on the same team. So, it was one of those moments where their backs were up against the wall and his best was needed and he gave his best.”

It probably won’t take 45 and 15 out of James for the Cavs to beat this year’s Celtics team in Game 3, but it will be a road test just the same.

“It’s a very hostile environment,” James said. “People here they love the game, they see green. They only see green. That’s all they care about is their team and you respect that as a competitor going against them, a fan base like this.”

While Celtics fans are seeing green, the Cavs are waiting to see that look in James’ eyes again that he had for that Game 6.

“Oh yeah, I’ve been around that a couple times,” Love said. “I’m sure during this journey that we’re taking together right now that we’ll definitely see that again.”