Payton Pritchard continues his big day, leading Celtics past 76ers in preseason opener

Kristaps Porzingis made 5 of 7 shots and had 17 points. Jayson Tatum was 3 for 13 from the field and Jrue Holiday was 2 for 10.

Observations from the game:

▪ Celtics coach Joe Mazzulla on Saturday said not to read into his starting lineup decisions for the opening preseason game. And that disclaimer ended up being helpful Sunday, when All-Star point guard Holiday came off the bench.

The starting lineup was Tatum, Jaylen Brown, Al Horford, Derrick White, and Porzingis. Most of the Celtics have been working out together for weeks, and Holiday’s first practice was on Wednesday.

“We’ve got eight, nine starters, guys that could start, finish,” Mazzulla said. “And so the preseason is being able to just experiment with different lineups, and our guys are open-minded.”

Holiday still played 15 first-half minutes, just a tick below the other starters, so it’s not as if he was being limited. The guess here is he’ll find his way into the starting lineup before long. Boston closed the half with Holiday on the floor with the other starters in place of Horford.

“I think it’s just about time,” Holiday said. “Time on the court, getting a chance to play with them and see what’s going to happen, see where I’m supposed to be and where I’m going to be getting the ball, and things like that.”

▪ Even though the Celtics are NBA title favorites, there’s some uncertainty surrounding them because everything will look so different. Marcus Smart had been with the franchise as long as Brad Stevens has, and the franchise has never had a player quite like Porzingis.

The 7-foot-3-inch forward was the best on the floor for Boston during the first half. On defense, he bothered the 76ers in the paint with his length. On offense, he started the game by swishing a 3-pointer and going 4 for 4 from the field. He and Tatum appeared to be working on their two-man game a bit in the opening quarter, and they had good results.

“It’s super easy, honestly,” Porzingis said. “Those guys are so talented. Jayson draws so much attention that it opens things up for me and that’s a perfect scenario for me. So I’m looking forward to more of those two-man, three-man actions where it’s really hard to guard, because we don’t even know what we’re going to do. We’re freestyling it and playing off of each other. So it has to be pretty impossible for the other team to understand what’s going to happen.”

Porzingis doesn’t figure to be quite the lob threat that Robert Williams was, but he is so tall and long that it doesn’t take much to find him above the rim. Porzingis was fouled on one lob from Tatum before he converted one from White.

▪ Pritchard entered the game midway through the first quarter along with Sam Hauser and Luke Kornet, which figures to be the second unit early on. He missed a couple of good looks before he banked in a deep three that led to a 4-point play at the buzzer. That may have been the jolt that he needed, as he drained his next two second-quarter attempts from long range.

Pritchard padded his stats a bit with a fourth-quarter surge against the 76ers’ third string. With the firepower on this Boston squad, he should get plenty of open looks.

Mazzulla has spoken highly of Pritchard during the preseason, and the Celtics clearly showed their confidence in him when they chose him to help fill the void created by Smart’s exit and then handed him this valuable extension.

“What you saw tonight and what you’ll see throughout the year is just his mindset and his professionalism to just be prepared over the last three years,” Mazzulla said. “And guys like him, they get rewarded in some capacity. And as I said before, we’re going to rely on him to give us another layer of toughness, another layer of physicality, another layer of playing with the right mindset.”

▪ It seemed as if Mazzulla wanted his starters to end on a good note. With the exception of Holiday coming in for Horford, the other starters played deep into the third quarter. And with Boston trailing, 76-74, four subs went to the scorer’s table to check in. But on consecutive dead balls Mazzulla signaled for them to stay right there. Brown finished off his own 9-0 run, Boston took the lead, and the starters were finally pulled. Mazzulla also used a coach’s challenge on an acrobatic Oshae Brissett putback dunk with 1:36 left. It was unsuccessful.

▪ It’s certainly not reason for concern, but Tatum struggled on offense. He was 3 for 13 from the field, 0 for 4 from the 3-point line, and 7 for 9 from the foul line. His rough stretch came in the third quarter, when he badly missed an open look inside, left an open baseline look well short, then had his dunk attempt swatted down by 76ers guard Jaden Springer. Afterward, Mazzulla focused on Tatum’s physical play.

“Even on some of the missed layups that he had, I thought he went downhill with force,” Mazzulla said. “And so he’s doing a great job of just understanding where he’s going, what spots he’s going to get to at different spots of the game, and as long as he does it with physicality and be ready to make the right play.”

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him @adamhimmelsbach.