The problem with playing first-place Washington, according to Lynx coach Cheryl Reeve, is that there are so darned many leaks to plug.

Against the WNBA’s most efficient offensive team, every mistake hurts. You plug one leak on defense and another appears. You plug that, and here comes another. So many players who can score.

It all caught up to Minnesota on Friday night at Target Center.

Up six after three quarters, the Lynx lost 86-79 to Washington after being outscored 30-17 in the fourth. The Mystics (19-7) clinched a playoff berth by winning for a fifth straight time.

Minnesota? At 13-13 with the stretch run looming, Reeve tried hard to take the positives out of a hard-fought game, knowing there was no time to dwell on the loss with a road game Sunday at Seattle.

“We did a lot of good things throughout the game,’’ she said.

“But we had spurts where, defensively, we did things we didn’t want to do.’’

The Mystics, who beat the Lynx in Washington by 23 points less than a week ago, made 12 three-pointers — seven in the second half — and turned 19 Lynx turnovers into 23 points.

That is a combination that’s hard to overcome.

“The turnovers,’’ said center Sylvia Fowles, who scored 16 points on 5-for-6 shooting and had eight rebounds. “Seems like that’s the story of our life.’’

“That’s what killed us,’’ said rookie Napheesa Collier, who scored all 13 of her points in the second half.

The Lynx led by as many as 10 and were still up six entering the fourth quarter. That’s when things went south.

With the Lynx turning the ball over twice and missing six of eight shots, the Mystics opened the quarter on an 8-2 run to tie the game at 64 on Elena Delle Donne’s shot with just under five minutes left.

Danielle Robinson drove for a score, but Delle Donne scored again, then a Lynx turnover was turned into Arial Atkins’ fast-break basket and then another turnover led to another Mystics basket and Washington was up — for good — by four with 3:32 left.

The Mystics shot 10-for-18 and made three of six three-pointers while scoring 30 fourth-quarter points.

Delle Donne scored six of her 14 points in the final quarter and Natasha Cloud scored eight of her 13.

Atkins finished with 18 points and Emma Meesseman had 17 off the bench.

The Lynx were 5-for-14 in the final 10 minutes, with five turnovers turned into eight Mystics points. Damiris Dantas had 14 points, as did Robinson off the bench. Veteran Seimone Augustus did not score, playing just six minutes, none in the second half.

For all of that the Lynx were still within a point after Dantas hit a three-pointer with 2:29 left. Atkins scored at the other end, then Fowles was called for an offensive foul going for a missed shot at the other end, a call Reeve said, given the physical nature of the close game, baffled her.

Washington finished the game on a 12-6 run.

“It’s tough, but we think we had good parts of the game,’’ Robinson said.

“It was the turnovers that killed us. A team that shoots it that well? They’re going to capitalize.’’

Eventually, the Lynx couldn’t plug all the leaks that sprung in the fourth quarter, when three Washington players scored six or more points.

“They scored 30 points,’’ Reeve said. “It was not our best quarter.

“Which is unfortunate, because I felt we played a pretty good game.’’