LOS ANGELES — This wasn’t the first time the Boston Celtics lost a 13-point third-quarter lead in this building, and it certainly wasn’t as critical as the Game 7 loss to the Lakers in 2010.

But the swiftness with which the Clippers dropped the anvil on Boston’s heads Monday night is bound to leave a mark.

The Celtics, playing without Al Horford (elbow), surrendered a 31-point turnaround in less than 13 minutes, falling behind by as many as 18 before suffering a 116-102 defeat.

Isaiah Thomas had 32 points and Marcus Smart added 21, but even though the Celtics shot just 41 percent from the floor, the real story was at the other end of the court. The Clippers were able to hit 21 of their last 25 shots to close it out.

“I’m not concerned,” said a clearly unhappy Thomas. “It’s just the way we lost was unacceptable. We lost the game in the last 15 minutes of the game. We played a really good game up until the last 15 minutes, and that’s the players’ fault, the coaches’ fault. That’s everybody in this locker room’s fault. We could have done a lot better.

“Everything,” he said about the source of his frustration. “We should have won this game. We should have won (Sunday night). We can’t be experimenting in Game 63.”

Experimenting?

“You can watch film,” Thomas said. “You know what it is.”

He seemed to be clearly pointing to lineups that included James Young (minus-19 in 13 minutes) and small crews.

Thomas had 10 points in 8:34 in the fourth quarter. He played 35 minutes overall. The Celtics were up six when he came out in the third and down eight when he returned in the fourth.

On whether he told Coach Brad Stevens to put him back into the game, Thomas said, “For the most part I try to let him coach. He’s a very smart dude and he does a good job with the substitution patterns. But, like, tonight I didn’t say nothing to him. Maybe I should have but it is what it is. We’ll figure it out.”

The Celtics seemed to have done just that early in the second half. Before numerous vocal Boston fans, they made a move to take control in the third quarter when Thomas had half the points in a 14-3 run to a 66-53 lead. But soon it was all gone – their lead, their mojo, everything.

The Clippers counterpunched harder.

Chris Paul helped tighten things a bit before Jamal Crawford, 0 of 5 to that point, found his stroke. He hit 3-pointers from the top of the key and right corner, then pulled up on a break and drilled one from 29 feet.

“I could see it in his eyes,” said Avery Bradley. “He had the confidence, especially once he hit the 3 on me. I could see it in the next bounce when he had the ball in his hands. It’s hard to stop somebody with that much confidence that can score the ball like that. We have to do a better team effort, better job as a team, trying to contain a player like that.”

After taking their 13-point lead with 4:31 left in the quarter, the Celtics went 1 of 4 from the floor with four turnovers the rest of the period as the Clippers outscored them, 22-5. Los Angeles scored on nine straight possessions to carry a 75-71 lead into the fourth.

Young opened that period with a 3-pointer, but Crawford had two more buckets in a 9-2 Clippers spurt to their biggest lead to that stage, eight points.

The Celtics tried to rally and were still technically in it with a little more than eight minutes to go, but then DeAndre Jordan had three dunks and a layup in a 10-0 run that removed doubt from the equation.

“Obviously (Crawford) made some tremendous shots,” said Stevens. “That’s what he does. We sent them to the free-throw line too much probably, and then we weren’t scoring on the other end. So obviously they kind of flipped the script there at the end of the third.

“You all know from watching the NBA, 13’s nothing when you’ve got a team like that with their capability. And yeah, that went quick. We didn’t respond well but we’ll get better from it.”

With Golden State next on the docket, they need to do that quickly. But first they have to get over this one.

“We had control of the game,” said Thomas. “We were up 13 at one point, and how we ended the third quarter is how we played in the fourth quarter. They had the momentum. They were the more aggressive team. The refs were what they were. And it was all she wrote after that.”