Though his final stat line was unremarkable for a starting guard, Jrue Holiday was one of the most important players on the floor Sunday in the Celtics’ postseason opener.

Holiday (nine points, five assists, three rebounds, three steals) steered Boston at both ends during a dominant third quarter, helping turn a one-point halftime deficit into a 17-point lead against the Orlando Magic. The Celtics went on to win 103-86 at TD Garden to go up 1-0 in the first-round playoff series.

The Celtics scored 30 points in the third, and 22 of them came on baskets Holiday either scored (by going 3-for-3 from 3-point range) or assisted on. Defensively, the 34-year-old grabbed two steals and helped limit Orlando to 18 points in the quarter, much of which he spent hounding Magic stars Paolo Banchero and Franz Wagner.

“That’s the Jrue I love, you know what I mean?” said Jaylen Brown, who was on the receiving end of a long-range, fast-break lob from Holiday. “That’s the Jrue I remember competing against. Regular season is different from the playoffs. I know sometimes y’all forget that and think like, it’s the regular season, but you can see his intensity level is a lot different. You can see the physicality is a lot different, so we just take it one game at a time. But Jrue, he loves the environment just as much as I do. You could see him picking up guys and blowing through screens and just making plays. When we get that Jrue, it’s a good sign for us.”

Head coach Joe Mazzulla credited Holiday with shifting momentum back toward Boston after Orlando controlled the second quarter. He ramped up his defensive intensity and pushed the pace on offense, with each of his third-quarter 3-pointers coming within three seconds of a steal or rebound.

After Wagner dribbled the ball off his foot 4 1/2 minutes into the second half, Holiday scooped up the loose ball and immediately launched a three in transition that put the Celtics ahead 66-56. They led by at least nine points for the rest of the game.

“He was big-time, both sides of the ball,” said Derrick White, who shot 7-for-12 from deep to lead the Celtics with 30 points. “Taking on that challenge and just causing havoc, and then offensively, just making the right play every time. He just does so much for our team and just doesn’t care about any of the numbers and whatnot. It’s great to have him as a teammate.”

On the next two Orlando possessions, Holiday blanketed Banchero on a missed midrange jumper and then denied a post entry to Wagner, resulting in a Magic turnover. A minute later, he poked the ball away from Banchero, fed a pass inside to a driving Jayson Tatum and, after Tatum missed at the rim, buried a second-chance three off a Brown offensive rebound.

“His defense led to the offense,” Mazzulla said. “… When he’s aggressive for us, we’re a different team, and it takes everybody to do that. Tonight, it started from his defense, and he changed it for us.”

Banchero and Wagner combined for 59 points in the game, but Orlando’s 6-foot-10 centerpieces went 1-for-6 with four turnovers while being guarded by the 6-foot-4 Holiday.

“He’s an innate competitor, and sometimes he takes a back seat because of the type of guys that we have,” Mazzulla said. “I thought tonight, he put the team on his back from that passion and emotion standpoint, and that’s why Jrue Holiday is Jrue Holiday. So we’re lucky to have him. We’re going to need that every single night. But we do feed off his physicality and his presence.”

This was the type of dirty-work performance the Celtics have come to expect from Holiday, who, as Mazzulla noted, has sacrificed personal production to fit into Boston’s star-studded lineup. The three lowest points-per-game averages of his career have come in his rookie year in 2009-10 and his two seasons with the Celtics. He also had his second-lowest assist average this season, trailing only his rookie mark.

But as he proved throughout Boston’s championship run last spring, the annual All-Defensive honoree has a penchant for making the subtle, winning plays that are necessary for a team to succeed in the postseason.

“I think I just take whatever opportunity comes to me, whatever that might be,” Holiday said. “We have enough talent on this team where I don’t necessarily take it upon myself, but I think everybody has kind of that mentality where if I get a chance, I’m going to do whatever I can to carry the load. So for me tonight, it was defensively and trying to hound the ball, and hopefully I continue to do that.”