The NBA’s perfect team met the reigning champions on Tuesday night.

Something had to give. They weren’t the champions.

In the most anticipated game of the early NBA season, the Celtics ended Cleveland’s perfect 15-0 start in a 120-117 win over the Cavaliers in Boston. The Celtics dominated the first half and then held off a Cavaliers rally in the second half to secure the win.

The Celtics opened a 65-48 lead in the first half, stifling Cleveland’s best offense and three-point shooting while making 14 of 22 shots of their own from beyond the arc. Boston extended its lead to 79-58 early in the third quarter and appeared headed for a romp.

But Cleveland answered with a 30-11 run, sparked by Donovan Mitchell and Evan Mobley, cutting the Celtics’ lead to 90-88 late in the third. Then Jayson Tatum ended the quarter with a buzzer-beating 3-pointer to cut the Celtics’ lead to five points.

Cleveland continued to apply pressure throughout the fourth quarter, repeatedly cutting the Boston lead to two points. But the Celtics answered every time and never let the Cavs take the lead.

Tatum led the effort with 33 points, 12 rebounds, seven assists and two steals. He was one of six Celtics to hit multiple 3-pointers on 6-for-10 shooting from beyond the arc. All five Celtics starters scored in double figures, as Boston shot 51.2% from the field and 53.7% from 3-point range on 22-of-41 shooting.

Mitchell led the Cleveland rally, finishing with a game-high 35 points to go along with eight rebounds and three assists. Mobley added 22 points, 11 rebounds, six assists, one block and one steal.

Darius Garland, whose emergence as one of the league’s best guards helped fuel Cleveland’s start, had a miserable shooting night. He shot 3 of 21 from the field and missed all six of his three-point attempts in an eight-point, seven-assist effort.

A Cavs team entering the game hitting 15.5 three-pointers per game at a league-best 41.9% clip shot 10 of 29 (34.5%) from long range.

It provided a strong performance and a statement from the Celtics that they remain the premier force in the league. The icing on the Celtics cake? The game was part of the NBA Cup and avoided an 0-2 start in group play after Boston lost the cup opener to the Hawks last week.

A historic streak comes to an end for the Cavaliers. Cleveland’s 15-0 start is tied with the 1993-94 Houston Rockets and the 1948-49 Washington Capitols for the second-best in NBA history. Golden State’s 24-0 start in 2015-16 remains comfortably the best of all time.

Now sitting at 15-1, the Cavs can move on to the second phase of their season. The unexpected quest for history is over and the extra pressure that comes with each game is lifted.

And there’s no shame in losing to the Celtics in Boston. They aren’t the first quality team to fall victim to a three-point barrage from these Celtics on their home court.

The next test for the Cavs is how they respond to the reset. Their perfect start was backed by advanced analytics that indicate the 15-0 record was no fluke and that this Cleveland team is a legitimate title contender.

But the championship path runs through Boston until another team proves otherwise. The Cavaliers have four games against the Pelicans, Raptors and Hawks before getting their next opportunity at home against the Celtics on December 1.