BOSTON — Preparing for the latest elimination game of his remarkable career—the latest Game 7 in this incredible run of brilliance—LeBron James seemed…different.

Those who have been with him for many of these referendum games, these moments that would somehow define his career one way or another, hadn't seen him quite like this before.

"Calm," a team source told Bleacher Report.

To those who have witnessed the better part of this 15-year masterpiece, which he continued carving Sunday night by leading the Cleveland Cavaliers to an 87-79 victory over the Boston Celtics to advance to his eighth consecutive NBA Finals, this was a departure.

Cleveland Cavaliers vs Boston Celtics ECF Game 7

They'd seen him appear "nervous" before elimination games in his days in Miami, a person who was around him in those days said. They'd seen him utterly focused in these moments during his second stint in Cleveland, as he was when facing a 3-1 deficit against Golden State in the 2016 Finals. At that time, a pregame check-in with LeBron yielded few words and a thousand-yard stare.

And up until Sunday night, that comeback against the Warriors had been James' signature achievement—a whirlwind of force and fury that he unleashed despite being asked to play 40-plus minutes in every game but one.

James didn't want to hear any of this, no matter how many different ways it was asked. But getting this Cavaliers team to the Finals—after the trades, the team meetings, long stretches with little or no consistent support and, finally, the loss of All-Star Kevin Love for Game 7 against the Celtics—may have been his finest hour.

"It's six seasons in one," James said. "It was five, but now it's six. I guess this is the last chapter for our team this season. It's been a whirlwind."

"Cedar Point" is what James compared it to, referring to the amusement park in Sandusky, Ohio, that calls itself "The Rollercoaster Capital of the World."

"This has been one of the most challenging seasons I've had," James said.