BOSTON – Celtics center Kristaps Porzingis had started 472 of 473 games in his career, playoffs included, prior to Game 1 of the NBA Finals.

Coming off the bench for just the second time in his career and playing in his first game since sustaining a calf injury April 29, Porzingis scored 20 points, including 18 in the first half, and added six rebounds and three blocks as the Celtics defeated the Dallas Mavericks 107-89 Thursday.

“Getting on the court (and) getting that kind of support was unreal,” Porzingis said of the Celtics fans. “The adrenaline was pumping through my veins and that definitely helped.

“Obviously it wasn't ideal that I was out for such a long time, but I did everything I could to prepare mentally for this moment coming back and it paid off and we got the job done tonight and had a good game and happy about the result.”

Though Porzingis, who spent two-plus seasons with Dallas, missed more than a month of the playoffs, Celtics coach Joe Mazzulla wasn’t worried.

“I know the storyline has to be ‘What's he going to look like because he was off for a month?’ ” Mazzulla said. "But that's what he's been doing his whole career. He's a great player. He's been great for us. The reason why we are here is because of what he's done. It doesn't matter how long he takes off, the guy is going to make plays because of how talented he is and the work he puts in.

“What he did for us tonight was big and we need that for the rest of the series.”

The Celtics didn’t "miss" Porzingis in that they still reached the NBA Finals with Porzingis sidelined due to his right calf injury.

But the Celtics, who acquired Porzingis from Washington in a 2023 offseason trade, missed his production, and that was evident in Porzingis’ return against the Mavericks. Mazzulla told Porzingis he planned to use him as a reserve.

“From day one I came here and I said I'll do whatever it takes to help this team win,” Porzingis said. “This, it made sense. I didn't care. I didn't care. I knew I could prepare to come off the bench, which is something different for me, and that's what I did and stepped into that role and embraced it and had a good game.”

He is the fourth player since 1970-71 to score at least 20 points off the bench in his first Finals game, joining Derrick White (21 points in 2022), Fred Brown (30 points in 1978) and Phil Smith (20 points in 1975). He is also the first player in a Finals game to play 22 minutes or fewer and score at least 20 points, collect at least six rebounds and block at least three shots, according to basketball-reference.com.

Coming off the bench, Porzingis was the early star. He entered the game with 7:17 left in the first quarter and scored 11 points on 4-for-5 shooting.

“I was so in the moment and enjoying the moment and the crowd and everything,” he said. “It’s like a blur to me right now. I have to rewatch the game, but I was completely just in the game. That's the best feeling. Like, I had the most fun, and I hope to have more of those moments going forward.”

The Mavs tried several defenders on the 7-foot Latvian, but he continued to make shots. During a two-minute stretch late in the first quarter, Porzingis made a dunk, blocked a shot, made a 16-foot jump shot, made a 3-pointer and blocked another shot that led to a Sam Hauser 3-pointer.

“He was just making play after play. He’s back, there’s no question about it,” Celtics star Jaylen Brown said.

With Porzingis on the court alongside Brown, Jayson Tatum, Derrick White and Jrue Holiday, the Celtics have the best five-man rotation in the league offensively and defensively.

On Wednesday, Porzingis caused consternation when asked what he expected from himself by answering, “It's tough to say. I haven't played. I haven't played for a while. Tomorrow will be my first real minutes in a while.”

He explained his answer after Game 1.

“All these thoughts like went through my mind in that moment,” he said. “Like, what do I answer? I want to say I'm fine, but obviously I haven't played. I haven't been out there. I haven't had the feel of like, am I 100%?

“But tonight, was an affirmation to myself that I'm pretty good. Maybe I'm not perfect, but I'm pretty good and I can play like this and I can definitely add to this team.”