In-season tournament: Pacers beat Celtics in quarterfinals with Tyrese Haliburton's first triple-double.

Tyrese Haliburton's first triple-double was timely. A big second-half performance by Haliburton helped the Indiana Pacers beat the Boston Celtics 122-112 on Monday night in the NBA's in-season tournament quarterfinals.

This win advances the Pacers to the tournament semifinals in Las Vegas on Thursday. Haliburton added to his outstanding season with 26 points, 13 assists, and 10 rebounds in the victory.

After closing the second quarter on a 12-2 surge, the Celtics led 55-48 at halftime at Gainbridge Fieldhouse. The Pacers took the lead in the third quarter courtesy to Haliburton's strong start.

The Pacers' first 19 second-half points came from Haliburton. Suddenly, the seven-point halftime deficit was gone. After outscoring Boston 37-23 in the third quarter, the Pacers led by seven heading into the fourth quarter.

However, that lead slipped. Midway in the fourth quarter, the Celtics tied again. In the last two minutes, Haliburton scored a four-point play with a huge 3-pointer to put the Pacers up four.

For his triple-double, Haliburton shot 10-of-18 from the field and 5-of-11 from outside the arc. The 23-year-old former Iowa State star entered Monday night averaging a career-high 27 points and 11.8 assists.

Myles Turner had 17 points and 10 rebounds, while Buddy Hield had 21. Five starters scored in double digits, while the Pacers shot over 47% from 3-point range.

In the defeat, Jayson Tatum led the Celtics with 32 points and 12 rebounds. Jaylen Brown scored 30 and grabbed nine rebounds, while Derrick White scored 18.