BOSTON — With another Game 7 victory at stake, LeBron James would not miss. He would not sit out. And he would not be denied an eighth straight trip to the NBA Finals.

The four-time league MVP scored 35 points with 15 rebounds and nine assists on Sunday night, leading the Cleveland Cavaliers to an 87-79 win over the Celtics and eliminating Boston from the Eastern Conference finals in the decisive seventh game.

In the first close game of the series — and the lowest-scoring — James played all 48 minutes and had 12 of his points in the fourth quarter for his sixth straight Game 7 win.

The NBA Finals begin Thursday at either Houston or Golden State. The Rockets host the seventh game of the West finals on Monday night.

Jayson Tatum scored 24, Al Horford scored 17 and Marcus Morris added 14 points with 12 rebounds for the Celtics, who were looking to return to the NBA Finals for the first time since 2010.

Tatum had a dunk over James with 6:41 left — and stared down the Cavaliers star and bumped him with his chest — and then followed it with a 3-pointer that gave the Celtics a 72-71 lead. But that would be Boston’s last basket for more than five minutes while Cleveland went on a 15-2 run to put the game away.

James and Horford embraced after the buzzer, then the Cavaliers donned NBA Finals hats and Eastern conference championship shirts before shuffling off the court to receive their trophy.

It’s not the one they want.

James has been in the finals every year since 2011 — four with Miami, and now four straight with Cleveland.

This might be his weakest supporting cast year.

He had to do it without Kevin Love — Cleveland’s only other all-star — who sustained a concussion in Game 6 and was replaced in the lineup by Jeff Green. Making his first start since the first-round opener against Indiana, Green scored 19 points and added eight rebounds — the star of James’ starless supporting cast.

The Celtics have had more time to get used to their injuries: Gordon Hayward has been out since the first game of the season, and Kyrie Irving has been sidelined since March. With the rookie Tatum and second-year Jaylen Brown, Boston established itself as the team of the future in the East.

But the present still belongs to James.

And, for now, that means Cleveland, too.

ADMIRING HIS WORK

The Celtics led by as many as 12 points in the first half, and they had a 51-47 lead midway through the third quarter when James hit a long 3-pointer and then Green made a 3 of his own. James hit Tristan Thompson for an alley-oop to give Cleveland a 55-51 lead, but then James threw the ball away and sent Terry Rozier off on a fast break.

James tracked the Celtics guard from the far sideline, timing his attack. When Rozier went up for the lay-in, James blocked it off the backboard and right to Green. James did not run back down the court, resting up while Green drew a foul at the other end and made one free throw to give the Cavaliers their biggest lead of the game.

TIP-INS

Cavaliers: Shot just 2 of 17 from 3-point range in the first half, making three of their first 22 shots from long range before James and Green connected on back-to-back attempts midway through the third quarter.

Celtics: Paul Pierce, whose number was retired by the Celtics this season, cheered the team on from courtside. … Rapper 21 Savage was also at the game. … Boston was 7 for 39 from 3-point range, with Rozier missing all 10 of his attempts.