Boston’s Jaylen Brown takes a shot during the Celtics’ 95-92 loss against Orlando on Sunday in Boston. Michael Dwyer/Associated Press

The Boston Celtics blitzed through the NBA, storming to the best record to start the season behind elite 3-point shooting. It was contagious throughout the roster. But over the last week, the script has flipped, and almost all of their shooters have gone cold at the same time. How is that possible?

“That’s just the NBA,” Celtics forward Jaylen Brown said. “That’s just how the journey goes sometimes. …

“You thought we were just going to shoot lights out for the whole season? (Expletive), I wish. It just never goes like that. But that’s a part of why you love basketball, why I love basketball.”

The Celtics are naturally reverting to the mean when it comes to 3-point shooting, but they couldn’t have expected this. After shooting 40 percent from deep through their first 26 games, the Celtics have gone inexplicably cold. Over their last five games, four of them losses, the Celtics have gone 63 for 220 from downtown, just 28.6 percent. Their three worst shooting performances of the season have come in the last week.

What’s gone wrong? Celtics interim coach Joe Mazzulla can’t quite explain it.

“I don’t know,” he said. “I think over the course of the season we shot the ball so well to start that there’s naturally going to be a small decline. We just have to maintain our confidence and our trust. We have really good shooters, so just have to stick with it.”

Even in the midst of their shooting slump, Mazzulla said the Celtics have stuck with their principles on offense to create spacing and produce open looks.

They’re simply just not knocking them down. But Marcus Smart said Sunday that he thinks the Celtics are pressing, and the numbers are reflecting that.

Brown – who scored 24 points and went 2 for 10 from long range – doesn’t think the Celtics are pressing. He’s not concerned because he thinks they’re still playing the right way offensively.

“I think we got a lot of easy shots,” Brown said. “The amount of assists we had tonight, I didn’t think were indicative of how we were playing the game. The ball was moving around, guys got open looks and open shots. It was just one of them nights where they didn’t go down.

“But we got whatever we wanted. I missed a lot of shots that I could make and were open. A lot of our guys missed shots that we make that were open. So we’ve got to just keep encouraging to take those shots. But I felt like it was just one of those games where I felt like a lid was on the rim.”

JAYSON TATUM was out for the Celtics on Sunday due to “personal reasons.” It was just the second time the Celtics star has missed a game this season. Mazzulla didn’t elaborate on Tatum’s status or if he may be back when the Celtics return to action Wednesday against the Pacers.

“It’s a personal thing,” Mazzulla said.

AFTER A WILD scramble for a loose ball in the closing seconds that resulted in a Magic possession, Smart inadvertently bumped heads with Orlando’s Kevon Harris as he argued with an official. Smart started bleeding above his eye, and covered it up by wearing a black headband for the rest of the game.

Moments later, the point guard dove to the floor for a loose ball. He was just fine.

“Head’s OK. Eye’s a little sore, but it’s part of the game,” Smart said. “I’m good, they cleared me. No concussion, thank God.”