Boston’s Derrick White blocks Denver’s Christian Braun during a preseason game Friday in Abu Dhabi, United Arab Emirates. Martin Dokoupil/Associated Press

The Celtics came out on top Friday in an international preseason battle between the two most recent NBA champions.

Boston defeated the Denver Nuggets 107-103 at Etihad Arena in Abu Dhabi to open its exhibition slate.

Payton Pritchard scored a team-high 21 points – 18 on his six 3-pointers – and fourth-quarter contributions from deep reserves Jordan Walsh, JD Davison and Drew Peterson helped the Celtics secure the win.

Coach Joe Mazzulla used nearly his entire expanded roster and leaned into the 3-point-heavy approach that defined Boston’s offense during its 2023-24 title run. The Celtics attempted a 61 3s, even as most of their players struggled to find their stroke as they reacclimated to game action. Pritchard was 6 for 12 from 3; his teammates were a combined 14 for 49 (28.5%).

The Celtics opened with four of their usual five starters: Jrue Holiday, Derrick White, Jaylen Brown and Jayson Tatum. Luke Kornet got the nod over Al Horford at the center spot, which will be occupied by Kristaps Porzingis once he makes it back from offseason leg surgery. (Porzingis, who made the trip to Abu Dhabi, is targeting a December return.)

Horford, 38, was given the night off as he prepares for his 18th NBA season. Mazzulla called it a “coach’s decision” in his postgame news conference, saying he didn’t feel like the uber-experienced Horford needed to play.

Xavier Tillman subbed in for Kornet after six minutes. The rest of Boston’s starters all played the entire first quarter.

Most checked back in midway through the second, with the exception of the 34-year-old Holiday, who logged just the one 12-minute shift. The veteran guard – the oldest of three Celtics players who competed in the Olympics this summer – went 2 for 7 overall and 0 for 4 from 3.

The other two Olympians keyed one of Boston’s best first-half sequences. White sandwiched a 3-pointer and a driving layup around a Tatum 3 and offensive rebound. That 8-0 run gave the Celtics their first lead of the game, 21-20.

Tatum led all starters with 12 points and five assists to go with six rebounds, including three offensive boards. It wasn’t his most efficient outing (4 for 11), but he hit 42.9% of his 3s (3 of 7) – a big improvement from where his outside shot was during last season’s playoffs and the Olympics. Tatum worked during the offseason to clean up his shooting mechanics, so his effectiveness there will be worth monitoring as Boston’s Oct. 22 season opener approaches.

White and Brown finished with nine and eight points, respectively, both shooting 3 for 9. Both were impactful defensively, as well, combining for three steals, two blocks and two additional forced turnovers under the basket.

Brown was visibly shaken up after colliding with Nuggets wing Vladko Cancar late in the first quarter, but he later returned and looked no worse for wear.

Tatum, Brown and White played 19 minutes – all the in first half.

Boston’s second unit featured three core rotation players (Pritchard, Sam Hauser and Kornet) and two end-of-the-bench reserves who are vying for larger roles (Jaden Springer and Walsh).

Pritchard was the Celtics’ leading scorer in each of their first three games last fall, and he continued that trend Friday, pouring in 14 first-half points while going 4 for 8 from deep. It was a return to form for the backup point guard, who struggled from 3 in the NBA Finals outside of his two incredible buzzer-beaters.

He and Hauser operated almost exclusively from 3-point range, attempting just one two-point shot between them. Hauser lacked his teammate’s shooting touch in this one, going 2 for 8 to finish with seven points in 17 minutes.

Kornet was a quiet standout, grabbing 11 rebounds (four offensive) and showing good vision as a passer (three assists). He was a plus-12 in his 21 minutes, tied for the best mark of any Celtics player, along with Walsh and the defensive-minded Springer.

The Celtics were outscored by 13 points with Tillman on the floor, but his 2-for-3 showing from 3 was a promising development given his modest track record as a scorer.

Center Neemias Queta – another of Boston’s projected Porzingis replacements – played the first five minutes of the second half, sharing the floor with Tillman. It was a rough stretch for the Portuguese 7-footer, who committed two quick fouls and had some issues with positioning on both ends of the floor. Queta also took a hard shoulder to the face from Russell Westbrook while fighting for a loose ball.

Mazzulla dug deeper into his bench in the fourth quarter, inserting two-way players Davison and Peterson and first-round draft pick Baylor Scheierman to open what proved to be an entertaining final frame.

Walsh, the Celtics’ second-round pick last year, made two of his three fourth-quarter shots, including a 3-pointer, and dished out three assists. He also blocked three shots earlier in the game. It was an encouraging outing from a player who spent most of his rookie season in the G League and did not impress in this year’s Summer League.

Fellow G Leaguers Peterson and Davison combined for 17 fourth-quarter points, with the latter icing the win with four late free throws. The 6-foot-1 Davison also had a key block with 88 seconds remaining.

Scheierman’s preseason debut, meanwhile, was one to forget. The 24-year-old Creighton product clanged his first 3-pointer off the top of the backboard, air-balled his second, missed a layup in transition, turned the ball over on an errant pass to Queta, and was whistled for a foul on a failed attempt to draw a charge.

Veteran wing Lonnie Walker IV, who’s with the Celtics on an Exhibit 10 tryout contract, didn’t see the floor until Mazzulla’s final round of subs. Walker, second-round rookie Anton Watson and Ukrainian big man Dmytro Skapintsev played the last four-plus minutes, along with Peterson and Davison, with Ron Harper Jr. also getting some run in the closing seconds.

Boston and Denver will meet again at 10 a.m. Sunday before both teams return home.

NOTES: Brown briefly addressed the crowd before tipoff, including a few sentences in Arabic. The Celtics star said last week that he spent a “large portion” of his offseason in the Middle East and now considers the area an “extended home” for him. … This was the Celtics’ first game outside of North America since 2007, when they played exhibitions in Rome and London to kick off a season that ended in an NBA title. One of the headliners of that team, Kevin Garnett, was in attendance Friday.