The Timberwolves locker room was quiet. And, for a quite a long time after Monday night’s game with the Boston Celtics ended, mostly clear of players.

This one was hard.

The Wolves showed the Target Center fans a new wrinkle in a 99-93 loss to the Celtics. A team that had struggled so much in the third quarter this season waited until the fourth Monday. But the result was the same.

“Every time, after a game, most of the time we’re talking about the third quarter,” said center Karl-Anthony Towns, who had 29 points, 18 rebounds, three assists, two blocks and one big case of frustration.

“And it seems the third quarter was the fourth quarter. We have to squash that. We can’t just move the third quarter to the fourth quarter.”

In an absolutely stunning reversal, the Wolves played very well while building a 10-point halftime lead. The team came out the locker room and grew that lead to 13 after three. And then?

“Laid a damn egg,” Zach LaVine said.

Isaiah Thomas scored 29 points, nine coming at the line. But, through three quarters, the Wolves had kept him off the line and under relative control. Al Horford scored 20 and Avery Bradley 13. But it was a group of mainly reserves that started this big Boston comeback.

Up 13, the Wolves were outscored 31-12 in the fourth. A 17-0 Boston run to started the quarter, in which the Wolves failed to score until Towns’ three-point play 6:42 in.

The Wolves made five of 25 shots in the fourth quarter, missed 10 of 11 three-pointers and allowed the Celtics to hit half of their eight threes.

Coach Tom Thibodeau said the team, this time, kept moving the ball on the offensive end. And the Wolves did get a lot of open looks at threes. They just didn’t fall. Towns, Andrew Wiggins and Gorgui Dieng were the only Wolves players to score in the final 12 minutes.

Wiggins finished with 14 points, but was 5-for-18 overall and 0-for-5 on treys. Dieng had 20 points and 10 rebounds. LaVine got 11 points but was 0-for-7 from three, 0-for-5 in the fourth.

“It’s frustrating, and I’m really disappointed in myself,” LaVine said. “We were playing great, we needed to win that. It was in our hands, and we pretty much threw it out like a piece of paper.”

For the Wolves (4-9) it’s back to the drawing board.

“It just shows you can never let your guard down,” Thibodeau said. “You have to strive to be a 48-minute team. We’re not doing that right now. We have to get back in, work, concentrate. We have to improve. We didn’t close out. For three quarters, I thought our defense was pretty good. They were shooting a low percentage, the [three-point] line was covered. Rebounding was good. But it doesn’t take much for a team to get on track. Once they got a couple they started getting good looks, and we started scrambling.”

This when the Wolves were a plus-12 on rebounds, scored 58 points in the paint and more than doubled up the Celtics on second-chance points.

None of that means much as the Wolves head out for a three-game road trip.

Frustrating? “It is,” Dieng said. “Seriously, it is. We put a lot of time and effort into it, and it slips away all the time.”