The midseason break for the Olympics seemed to have done the Washington Mystics some good Sunday. They were mostly healthy. They were efficient on offense. They played dogged defense. And they led one of the WNBA’s top teams by 21 points on the road late in the third quarter.

And then the Mystics collapsed.

Washington stopped playing defense, and anyone not named Ariel Atkins struggled to put the ball through the basket. With 4.6 seconds remaining, Chelsea Gray came off a screen and hit a step-back midrange jumper over Tina Charles to give the Las Vegas Aces their first lead since the 8:17 mark of the first quarter. Atkins missed a deep three-pointer at the buzzer, and Washington fell, 84-83.

“Those are the ones that stay with you,” a particularly measured Mystics Coach Mike Thibault said.

The fourth quarter was a disaster for the Mystics (8-11) by any measure. They were outscored 29-14. They shot just 37.5 percent from the field and 22.2 percent from three-point range after the offense hummed in the first half. Charles, the league’s leading scorer, struggled to get touches, and 2020 MVP A’ja Wilson and Liz Cambage finally found their footing. The Aces used a 20-5 run that started in the third quarter to cut the lead to four, then closed with a 11-2 stretch to put the game away.

Atkins missed a 27-foot jumper from well beyond the top of the arc in an attempt to win the game after the Aces took away Charles as the first option.

Atkins and Charles led the Mystics with 20 points apiece, and Myisha Hines-Allen finished with 16 points and eight rebounds. Natasha Cloud added 11 points and 10 assists.

Wilson finished with 20 points and 14 rebounds for the Aces (16-6). Cambage added 17 points, and Jackie Young totaled 14.

“It’s upsetting. I feel like we kind of had a similar situation back at home when we played them,” Atkins said. “We know how good we are. I think, for me, that’s the frustrating thing. We’re trying to find ways to put it all together for four quarters. I think that’s the consensus of what we all see. Yeah, we’re good. We know we’re good. We have to put it together for four quarters.

“As tough as that loss was, it doesn’t stunt our confidence. If anything, it’s gets us frustrated with ourselves a little bit. But I think it’s not a bad frustration. I think it’s a good frustration. I think we realize what we’re capable of. We saw it in action.”

Thibault said the Aces switched up their defense in the second half and used a bigger lineup. He also pointed to a 21-9 free throw disparity that slowed the game and took the Mystics out of their offensive rhythm, particularly in the second half. Thibault said he preached to the team all week that it couldn’t put the Aces on the foul line, and that’s exactly what happened. Las Vegas hit 13 of 16 free throws after halftime.

The Mystics also were frustrated by a travel called on Hines-Allen with 12 seconds remaining that looked like a legal hop-step. That set up Gray’s game-winner.

We went back to how we used to play into bad habits,” Hines-Allen said, “and got away from what we were doing well in the first half. A lot of our buckets in the first half were coming off defensive stops. So our defense, I think the second half, we let up a little bit. And this is a great team. You can’t let up on a great team like this because they can score from all positions.”

The Mystics fired away from long distance to take a 50-35 lead into halftime. The Aces didn’t make good decisions when the Mystics came off a pick and roll with shooters handling the ball and popping out to the arc after setting the screen. Six of the seven first-half threes came from Charles and Hines-Allen.

A 12-3 first-quarter run by the Mystics, capped by a Hines-Allen three from the right wing, set the tone. The Mystics extended the lead to 21 late in the second quarter on a three by Charles.

Eight players scored for Washington in the first half as the team shot 52.8 percent from the field and 46.7 percent from behind the arc. Washington didn’t have eight players available to play at times before the Olympic break because of injuries.

Las Vegas tried to use its size advantage early, but that didn’t work until the second half. The Aces didn’t have any players score in double digits in the first 20 minutes as Wilson, Cambage and Young were kept in check early. The Aces shot 44.1 percent in the first half.

The teams face each other again in Las Vegas on Tuesday.