Boston Celtics head coach Brad Stevens paid tribute to the "unbelievable" LeBron James after his team's game-seven loss to the Cleveland Cavaliers.

James led the Cavs to the NBA Finals as his 35 points, 15 rebounds and nine assists saw Cleveland past the Celtics 87-79 at TD Garden on Sunday.

The win saw James move into the Finals for an eighth straight season, and he will be eyeing a fourth championship when his team face either the Golden State Warriors or Houston Rockets.

Stevens had nothing but praise for James, highlighting the 33-year-old's incredible consistency.

"He's unbelievable," he told a news conference.

"I think we've played now until May 25 and May 27 the last two years and we started on September 25 and that's every day – every day that you're totally focused on this.

"He's gone past that eight straight times. It's ridiculous. And he does it at this level, with the pressure, with the scrutiny, doesn't matter, it's just unbelievable.

"Our goal, going into the series, was to make him exert as much energy as humanly possible and try to be as good as we can on everybody else, who are good players, and for the most part I thought we were pretty good at that.

"Multiple games, in TD Garden, we held them under 100 [points] – three games in the 80s – but he still scored 35. It's a joke."

Despite their defeat, the Celtics were lauded for their run to the Eastern Conference finals – one managed without two of their stars in Kyrie Irving and Gordon Hayward.

While acknowledging the disappointment, Stevens also praised his team for their run.

"Every ending is tough. I guess that's for all 29 teams that don't win it and no matter how good of a season you had, the ones that don't end with you winning a championship, it's going to be a disappointing ending," he said.

"But it was a pretty incredible run by an incredible group of guys and an absolute pleasure and privilege to be around them every day."