Jaylen Brown scored 22 points, Kristaps Porziņģis added 20 in his first game in more than a month and the Boston Celtics powered past the Dallas Mavericks 107-89 on Thursday night in Game 1 of the NBA finals.

Derrick White finished with 15 points for Boston, which led by 29 points in the first half and connected on 16 three-pointers in a powerful start to its quest for an 18th NBA title.

Porziņģis, who had been sidelined since 29 April with a strained right calf, came off the bench and provided an immediate spark, adding six rebounds and three blocks in 21 minutes. Six Celtics finished in double figures.

Dallas cut the deficit to eight points in the third quarter, but Boston quickly pulled away again.

Luka Dončić led Dallas with 30 points. PJ Washington added 14 points and eight rebounds. But Dallas couldn’t find offensive consistency beyond that, totaling just nine assists on their 35 field goals for the game.

Former Celtic Kyrie Irving struggled throughout, finishing with 12 points. He received a loud and extended chorus of boos Thursday when he was introduced before the game. It continued throughout the game whenever he touched the ball.

The treatment came after Irving sparred with Boston fans and was fined for using an obscene gesture during a 2022 playoff visit to TD Garden.

The Celtics, seeking their first championship since 2008, showed little rust from their 10-day layoff after sweeping the Indiana Pacers in the Eastern Conference finals.

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They flowed with energy throughout, sharing the ball in the halfcourt and getting the ball to shooters for open threes. They also attacked the interior of the Dallas defense and got to the rim for several dunks.

Meanwhile, apart from Dončić, who shot 12 of 26 from the field, Dallas struggled early to get into its sets and couldn’t find a consistent groove offensively.

The Mavericks led by one midway through the first quarter. The Celtics responded by outscoring them 44-16 to make it 58-29 in the second.

Things changed over the next 12 minutes of game action when Dallas used a 35-14 run, including 15 points by Dončić, to cut Boston’s lead to 72-64. But Boston ended the third quarter with a 14-2 spurt to get it back up 86-66 entering the fourth.

Dallas had just five assists through the first three quarters, the fewest any NBA team has had, in any game, through 36 minutes in the last three seasons.

Porziņģis ended his 10-game hiatus when he came off the bench with 7:17 left in the first quarter in place of starter Al Horford. With the exception of a white compression sleeve on his right leg, it was hard to tell Porziņģis was coming off an injury.

He got into the mix quickly, knocking down a pair of free throws after being fouled by Dončić. A possession later, the Latvian connected in his first field goal when he dropped on a short jumper over Dončić.

He wasn’t done.

Minutes later he got loose in the paint for a two-handed dunk over Derrick Lively. On Dallas’ next possession, Porziņģis was there to swat away Jaden Hardy’s layup attempt. The Celtics pushed the ball up the court and got the ball back to their big man, who calmly buried a 16-footer.

It was part of a 17-5 surge by Boston over the final 5:24 of the quarter that saw Porziņģis go 4 for 5 from the field, score 11 points, block two shots and grab three rebounds. Boston carried a 37-20 lead into the second quarter.

Porziņģis finished the half with 18 points on 7-of-9 shooting.

• NBA finals
• Dallas Mavericks
• Boston Celtics
• Basketball
• NBA
• US sports
• Luka Dončić