Chris Bosh shook his head in disbelief. “The best I’ve seen; one of the best this league has ever seen,” he said after his teammate’s surreal night.

Pat Riley walked through the corridor of TD Garden leading to the locker rooms, nodding. “He was just so dialed in,” the Miami Heat patriarch began. “Maybe I should give him one of those old phones.”

Besieged by the most gifted player in pro basketball in Game 6 of the Eastern Conference finals on Thursday night at TD Garden, the Boston Celtics had the best ticket in the building to watch LeBron James deliver the most scintillating big-game performance of his career.

Forty-five points, 15 rebounds and five assists — and all the humiliating, in-your-eye, rock-and-fire jumpers Kevin Garnett, Paul Pierce and Rajon Rondo could stomach — James single-handedly swung the pendulum back to Miami for an NBA Finals-or-bust Game 7.

Hubris and the Heat 98, Old-as-Dirt Celtics 79.

The problem with one-game referendums in the NBA — Kobe Is Too Old, the Spurs are a Championship Lock and, of course, LeBron Wilts When It Matters — is there always is another game, another possession to step back and release a pretty, label-killing jump shot.

And suddenly the complacent, cocksure kids who took their talent for granted — to the point of nearly getting run off the floor by a bunch of creaky-kneed geezers reeking of menthol gel and heat rubs — just remembered a reassuring truth:

They have LeBron James and the old Celtic heads don’t.

This was supposed to be the night immaturity and bravado were served again; the night when all the fourth-quarter liabilities of an otherwise indestructible player would do in him and his team for another season.

But the Celtics forgot something important as they tried to close out the Heat after stunningly getting out of Miami with Game 5 and a 3-2 lead earlier this week: If you let LeBron get out to a healthy lead, what he does in the fourth quarter doesn’t matter.

Has any all-time great ever been so magnificent with a lead and so maddening without it?

Stepping back, rhythmically rattling in shots, placing the ball on the tips of teammates’ fingers, finding Dwyane Wade through itty-bitty crevices in mounds of muscle, James played maestro on a basketball floor on Thursday.

LeBron James put the clamps on Paul Pierce, who made only 4 of 18 field goals for nine points. (Elise Amendola/AP)

“I was in such a zone, I wasn’t paying attention,” he said when asked if he realized how demoralized the Celtics looked.

LeBron had 30 points at halftime and 41 by the end of the third. A Garden crowd that had come to see the Celtics stun the favored Heat on their home floor sat there with their popcorn and beer, crestfallen, understanding the long odds awaiting a beaten-down Boston roster, which Coach Doc Rivers rested for much of the final eight minutes of the game.

One player was responsible for a team’s demise. With his season on the line — with perhaps his coach’s job on the line as well as the future of Miami’s Big Three — LeBron managed to turn in an absolute gem.

“I don’t get too far into sports-talk radio,” he said, playing down speculation he used criticism for motivation. “I don’t really hear the outside noise of what’s said about me or said about my team.”

He added, almost ominously: “I won’t regret Game 7. Win, lose or draw.”

LeBron came into Game 6 with baggage — a 2-6 mark in games in which his team faced elimination in Cleveland and Miami. Usually it’s older, wiser heads dispensing the hard lessons of defeat: Dirk Nowitzki and Jason Kidd a year ago, Boston Big Three in 2010, the seasoned Spurs in the 2007 Finals.

And here was the lesson learned: Three minutes left in the first half, the Celtics finally finding a rhythm, Ray Allen squaring up for what is still the purest jump shot in the game, his three-point swish bringing the Garden to a frenzy.

On the next possession, after a Heat misfire, Allen gets free on the right baseline, catches the ball. But just as he’s ready to rise and fire, he’s startled to see a 6-foot-8, 245-pound man in his grille; LeBron had traveled clear across the court to make sure Allen was not going to get that shot off. Every ounce of his determination was in the dead sprint to defend the marksman behind the arc.

That defensive play was as important as any offensive possession in the game.

Crackerjack theory of why the Heat didn’t wake up earlier in this series: Ever since they’ve been assembled, LeBron, Wade, Bosh and the rest of the organization have been addicted to drama.

From “The Decision” to every late-game collapse or success, it’s almost as if they wouldn’t know what to do with a 3-0 lead against an inferior team.

They’re Adversity’s Children, but they’ve yet to become Prosperity’s Adults.

Now LeBron gets his chance to grow up. He’s put his foot on a foe that appeared to have him down. If he is genuinely going to earn the right to show the world that Kevin Durant is not the best player in the game — and Durant may very well be, especially during these playoffs — then LeBron needs to deliver the series-ending punch Saturday in Game 7.

It’s the only way to change perception for good.

For Mike Wise’s previous columns visit