BOSTON (AP) — Kristaps Porzingis didn’t want to make predictions about how his body would respond heading into the NBA Finals after he spent more than a month on the sideline with a calf injury.

Just fine, it turned out.

Jaylen Brown scored 22 points, Porzingis made an immediate impact off the bench and added 20 and the Boston Celtics powered past the Dallas Mavericks, 107-89, on Thursday night, June 6, in Game 1.

Derrick White finished with 15 points for Boston, which led by 29 points in the first half and connected on 16 3-pointers in a powerful start to its quest for an 18th NBA title.

Porzingis, a 7-footer who had been sidelined since April 29, added six rebounds and three blocks in 21 minutes.

“Tonight was affirmation to myself that I’m pretty good,” Porzingis said. “I’m not perfect but I can play like this and I can add to this team.”

The last Celtics player to enter the court for pregame warmups, he said he received a jolt of energy from a home crowd, which erupted when he emerged from the tunnel.

“The adrenaline was pumping through my veins,” Porzingis said.

Celtics coach Joe Mazzulla wasn’t concerned about the layoff affecting Porzingis’ aggressiveness.

“That’s the KP that helped us get to where we are today,” Mazzulla said. “It doesn’t matter how long the guy is off, he’s going to make plays.”

All-Star Jayson Tatum finished with 16 points and 11 rebounds. Six players scored in double figures for the Celtics, who host Game 2 on Sunday.

“Getting back to this point and being here is really a big deal,” Tatum said. “But two years ago we won the first game and we know the outcome of that series. We still have a lot of work to do.”

Dallas cut the deficit to eight points in the third quarter, but Boston answered with a 14-0 run to quickly pull away again.

“That’s when the game started,” Brown said.

Luka Doncic led Dallas with 30 points. P.J. Washington added 14 points and eight rebounds. But Dallas couldn’t find offensive consistency beyond that, totaling just nine assists on its 35 field goals for the game. The Mavericks didn’t score 25 points in any quarter.

Doncic said the lopsided loss wouldn’t diminish the spirit of a team that lost the opening game in three of four series this postseason.

“Either you lose or you win,” Doncic said. “First to four, we’ve got to focus on the next 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.

“I thought it was going to be a little louder in here. I’m expecting the same thing (in Game 2). The crowd’s trying to get me out of my element,” Irving said. “It’s not the first time I’ve lost in Boston. I don’t want to make it a habit.”

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.