Aaron Nesmith took a transition pass from Tyrese Haliburton and dunked it over Al Horford. The former Celtic galloped around the court and chest-pumped Myles Turner as the rest of his Pacers teammates flooded the court to celebrate an imminent victory.

The Celtics proved they cared about the NBA’s inaugural In-Season Tournament with how they handled their final group stage game last week. They showed that mentality during stretches of Monday’s first ever quarterfinal game of the tournament. But ultimately, the moment meant more for the upstart Pacers.

In a playoff-like atmosphere, the C’s couldn’t get the job done on Monday night in Indiana. Jayson Tatum scored 32 points and Jaylen Brown added 30, but their worst habits haunted them again. They laid another dud in the third quarter. Too many turnovers piled up. And then the Pacers – led by Tyrese Haliburton – raised their game to another level in the second half, as they handed the Celtics a 122-112 loss and sending them home from the In-Season Tournament.

The Celtics will not be moving on to Las Vegas for the semifinals. Instead, they’ll return home for a regular season game on Friday night against the loser of Tuesday’s Bucks-Knicks tournament quarterfinal.

Haliburton recorded his first career triple-double – 26 points, 13 assists and 10 rebounds – and brought his best in the second half. He brought them back with a huge third quarter. And then – in a game that featured 16 lead changes and incredible shot-making on both sides – he made the difference late. He broke a tied game with a four-point play with 1:33 to go that sent the Pacers on a winning 9-0 run. He hit Buddy Hield for a 3-pointer, then his feed to Nesmith with 44 seconds sealed it.