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

Something had to give. It wasn’t the champs.

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

The Celtics opened a 65-48 first-half lead, stifling Cleveland’s league-best offense and 3-point shooting while hitting 14 of 22 of their own shots from beyond the arc. Boston extended its lead to 79-58 early in the third quarter and appeared on its way to a romp.

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

Cleveland kept pressure on throughout the fourth quarter and repeatedly cut the Boston lead to two points. But the Celtics answered every time and never allowed the Cavs to 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 a 6-of-10 effort 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 distance on a 22-of-41 effort.

Mitchell led the Cleveland rally and finished with a game-high 35 points alongside 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 has helped spark Cleveland’s start, had a miserable shooting night. He shot 3 of 21 from the field and missed all six of his 3-point attempts in an eight-point, seven-assist effort.

A Cavs team that entered the game hitting 15.5 3-pointers per game at a league best 41.9% clip shot 10 of 29 (34.5%) from long distance.

It added up to strong showing and a statement from the Celtics that they remain the league’s preeminent force. The icing on the Celtics cake? The game was part of the NBA Cup and prevented an 0-2 start in group play after Boston lost its Cup opener to the Hawks last week.

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

Now at 15-1, the Cavs can move on to the second phase of their season. The unexpected chase for history is no more, and the additional pressure that comes with each game is lifted.

And there’s no shame in losing to Celtics in Boston. They’re not the first quality team to fall victim to a 3-point barrage by these Celtics on their home court.

The next test for the Cavs is how they respond to the reset. Their perfect start was backed up by advanced analytics that suggest that 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 they get their next shot at the Celtics at home on Dec. 1.