The Mets hardly looked like a team that had pulled itself off the mat and back into playoff contention during Saturday’s ugly 9-5 loss to the Braves at Citi Field.

From a third straight subpar outing by Zack Wheeler, to poor baserunning and bad defense, many of the Mets’ weaknesses were on display in a second straight loss to Atlanta.

And to finish it off, Edwin Diaz left the game in the ninth inning with tightness in his upper back, adding to the Mets’ bullpen issues.

The outcome overshadowed Pete Alonso’s mammoth, record-tying homer that gave the Mets a one-run lead in the fifth.

The three-run shot made it 5-4, but Wheeler gave up an unearned run in the sixth, thanks to a two-base error by third baseman Todd Frazier, to knot the game.

Things only got worse in the eighth, when Atlanta went ahead for good.

Rafael Ortega lined a two-out single off Brad Brach that just eluded a leaping Joe Panik at second base. Pinch-hitter Billy Hamilton then singled before Ronald Acuna Jr. singled to left, scoring Ortega and giving the Braves a 6-5 lead.

But J.D. Davis held the ball too long in left and the speedy Hamilton came around to also score on the play, to put Atlanta up by two runs.

Davis said he got distracted by Acuna going far off first base. Hamilton took advantage of the mistake and kept running as Davis tossed the ball to Amed Rosario far too late.

“I looked at first as I released it to [Rosario] and [Hamilton] was already rounding third,’’ Davis said. “I should have just thrown it to [Rosario].”

Davis called it a “helpless” feeling.

The Mets also blew a chance to go up in the bottom of the seventh, when the game was still tied.

Jeff McNeil, in his first game off the injured list, delivered a pinch-hit double to open the inning.

Rosario, in the leadoff spot, tried to sacrifice McNeil to third, but didn’t get the bunt down.

“It’s a tie game and we wanted to get the runner over to third,’’ Callaway said. “Panik has a hot bat and we figured he’d get him in.”

Instead, McNeil was thrown out at third when Rosario hit a grounder to short. Rosario was then thrown out trying to steal second — by former Yankee Francisco Cervelli, in his debut with Atlanta that also included three hits — and the Mets failed to score.

There were other concerns, as well, as Diaz’s nightmare season continued when he gave up a solo homer to Freddie Freeman and left the game two batters later after being seen on the mound by the trainer.

Wheeler, who said he intended to make some adjustments after a pair of bad outings, didn’t show much improvement.

The right-hander has now followed up the two gems he tossed in his first games after the trade deadline passed and he stayed in Queens, with three clunkers.

He gave up five runs — four earned — and two homers in six innings and admitted he didn’t know why he has been so inconsistent.

The Mets got a run back in the third when Juan Lagares led off with a double and came around to score.

Lagares doubled and scored again in the fifth to make it 4-2.

They went ahead later in the inning when Alonso smacked a 451-foot three-run homer to center to give the Mets their first lead of the night, 5-4. It was also Alonso’s 41st homer of the season, tying the franchise mark shared by Carlos Beltran and Todd Hundley.

But it didn’t last, as the Mets lost for the fourth time in five games to Atlanta at Citi Field this season — and the first-place Braves won their seventh consecutive game.

“We’ve been extremely resilient all year and these two losses are tough, but all of us in this locker room are high character,’’ Alonso said. “We’ve come a long way to get here and we still have a really good opportunity ahead of us. … We’re still in a great spot. We need to win [Sunday] and take it into the next series.’’