BOSTON — In their first 15 games this season, the Orlando Magic never folded, even in losses.

There’s a first time for everything, apparently.

The Magic unraveled Monday night, and the result wasin the worst single-game offensive performance in team history. They set franchise single-game lows for points scored and field-goal percentage as they absorbed a 87-56 beatdown from the Boston Celtics at TD Garden.

“It didn’t start well, and it got worse as the game went on,” Magic coach Stan Van Gundy said.

“That’s the most dominating defensive performance, at least, that I’ve ever had against me. There’s no singling anybody out. It’s the first game, I think, in my career I’ve ever been through where literally not one guy played well. We didn’t play well. So there’s no finger-pointing, and it’s why you get dominated. Not one guy had a good night, and I’m foremost among them.”

Just how awful was it?

Orlando made only five baskets during the entire second half.

“They outplayed us,” point guard and co-captain Jameer Nelson said. “They played harder than us. They played tougher. One through however many we have on our roster, we couldn’t execute our offense. Defensively, we didn’t help each other. It was just a selfish game from everybody. It was just very selfish.”

But why did it happen?

Monday should have offered the Magic a golden opportunity to beat the Celtics.

Ray Allen sat out with an ankle injury. Rajon Rondo did not play because of a wrist problem. Even Mickael Pietrus, Chris Wilcox and Keyon Dooling were hurt.

And the rest of the Celtics had played the day before.

The Magic not only failed to take advantage of the situation. They imploded.

Avery Bradley, Boston’s second-year point guard, set the tone immediately by pressuring Nelson as Nelson brought the ball upcourt.

Bradley fired up his teammates, and he also appeared to unnerve Nelson.

“He seemed like he didn’t even want to bring the ball up,” Bradley said in a postgame interview with NBA TV. “I looked at him and he kept telling me throughout the game, ‘You know what, don’t pick me up, don’t pick me up.’ And that’s when I knew, if I brought pressure, he didn’t want nothing to do with it.”

Nelson finished with just five points and three assists, and he also turned the ball over five times.

Orlando stopped moving the ball. Players no longer attempted to make an extra pass or go to a third or fourth option.

Van Gundy said his team “panicked,” and everything became a one-on-one game. And, in a one-on-one game, the Magic (11-5) just couldn’t compete with the Celtics (7-9).

Orlando made just 24.6 percent of its shot attempts, setting a new franchise low for the worst field-goal percentage in a game. The previous low was 25.0 percent, set against the New York Knicks on Nov. 3, 2003.

The 56 points set a new Magic all-time low for a single game. On Dec. 4, 1996, the Magic scored only 57 points against the Cleveland Cavaliers.

Boston employed the same gameplan it has used against Orlando for several seasons now, often to devastating effect. The Celtics defended Dwight Howard one-on-one, which allowed Boston’s four other players to concentrate on Orlando’s perimeter shooters.

This time, instead of Kendrick Perkins or Shaquille O’Neal, the Celtics used Jermaine O’Neal, Kevin Garnett or even rookie Greg Stiemsma.

It still worked.

Howard scored 12 points on 4-of-6 shooting in the first quarter. After that, he missed his next nine shots and scored just six more points.

On Monday, the Celtics took control of the game in the closing minutes of the second quarter, ending the half on a 12-3 run.

Garnett and Paul Pierce each hit a pair of foul shots. Garnett followed with a layup, and Pierce sank a 3-pointer. Brandon Bass finished Boston’s run with a fadeaway jumper as he was fouled by Earl Clark, and then Bass converted the three-point play.

Garnett and Bass finished with 19 points apiece.

“We didn’t stay together,” Howard said. “We started blaming each other, and I have to do a better job of policing that — me being a captain of the team — and we’ll get better.”

The Magic mustered only 10 points in the third quarter.

The period ended with Garnett positioning himself just inside the top of the arc, shooting just over Howard’s outstretched hand and banking-in a long jumper to put the Celtics up 69-46.

Howard said the entire team’s energy was poor, even his own on occasion. Howard said Garnett beat him up and down the floor on a couple of plays.

Meanwhile, Orlando just couldn’t get any shots to fall.