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BOSTON — Under the banners won and jersey numbers worn by some of the NBA’s most famous “sixth men” — Frank Ramsey, John Havlicek, Kevin McHale, Bill Walton — Kristaps Porzingis etched his name for a night into their ranks.

Playing in his first game in more than five weeks, the 7-foot-2 center came off the bench to spark Boston to its 107-89 victory in Game 1 of the Finals Thursday at TD Garden.

The moment: Working in reserve for only the second time in 473 games over his nine-year career, Porzingis — back from a strained right calf — entered to a roar with 7:17 left in the first quarter and his team trailing 12-11.

“Getting that kind of support was unreal,” he said later. “The adrenaline was pumping through my veins.”

The impact: Over what remained in that quarter, Porzingis lit up the Mavericks for 11 points. He outscored Dallas in Boston’s 26-8 close to that period, adding seven more points in the 5:41 he played in the second quarter.

Porzingis was plus-15 in 13 minutes by halftime and had outscored the entire Mavericks bench 20-4 through three quarters. That included a sequence deep in the third after Dallas had scratched back to within 72-64. Two trips later, Porzingis attempted a 3-pointer, missed, and broke toward the basket. Jayson Tatum grabbed the rebound and passed it back to Porzingis for a slam. The Celtics kept going for a 14-0 run and had their cushion back at 86-66 heading into the fourth.

His size helped defensively, too, contending with Dallas’ big options up front — Daniel Gafford and Dereck Lively II combined for just 10 points and eight rebounds — while clogging space where the Mavs’ dynamic guards generally like to drive.

Let’s not neglect the emotional jolt Porzingis brought to the Celtics and the sold-out arena. It was one thing to make it through 37 days of the NBA postseason without their starting center — they went 9-1 in his absence against the Miami Heat (against whom he got hurt), Cleveland Cavaliers and Indiana Pacers.

But it would be a greater challenge for Boston to cope with Luka Doncic, Kyrie Irving and Dallas’ pogo-stick centers without Porzingis’ three levels of scoring and rim protection.

What they’re saying: “It’s kind of like a blur to me right now. I have to re-watch the game, what happened and stuff, but I was completely just in the game. That’s the best feeling.” – Porzingis on the performance.

“Listen, I know the storyline has to be, what’s he going to look like because he was off for a month, 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 gong to make plays because of how talented he is and the work he puts in.” – Celtics coach Joe Mazzulla.

“I know he knew I was going to be fine with whatever, you know, so he just told me, what do you think, like, about this. And I said, of course, like, let’s do it. And that’s it. Wasn’t no big deal and I trust Joe and he trusts me.” – Porzingis on Mazzulla talking with him about the bench role.

“KP got to an unbelievable place there early in the first half, in the first quarter, and I just felt like it really got us going and took us to another level as a team.” – Celtics center Al Horford.

“It was amazing. Nobody’s more proud and more excited for him than I am. … He’s a big reason why we’ve been the best team in basketball record-wise, at least, and having him back and him playing well and to that level he was during the season is so important for us because you got another defender, another shooter, out there that you have to respect.” – Teammate Jaylen Brown.

“It’s tough to not play for a month and then jump into the highest intensity game in the Finals. … I did everything I could to prepare for this moment, like mentally, and then just going out there and playing instinctually almost and trusting my body.” – Porzingis on wondering about rust, conditioning or his calf.

What’s next: The unknown is whether Porzingis can contribute at this rate for the rest of the series or even in Game 2 on Sunday (8 ET, ABC). Neither he nor anyone else knew late Thursday how his calf would respond after Game 1 or how it would feel in the coming days.

The Mavericks will adjust to what they saw from him and try to test his stamina, maybe his mobility, more than they did. It’s possible that the adrenaline Porzingis felt won’t be on tap like this next time.

In the best if-it-ain’t-broke-don’t-fix-it tradition, Porzingis likely will continue as the Celtics’ sixth man … for the franchise that invented the role.

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Steve Aschburner has written about the NBA since 1980. You can e-mail him here, find his archive here and follow him on X.

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