The Mets' Starling Marte dives safely under the tag by Arizona Diamondbacks...

The Mets' Starling Marte dives safely under the tag by Arizona Diamondbacks catcher Adrian Del Castillo on a sacrifice fly out by Pete Alonso in the sixth inning of a game on Wednesday in Phoenix. Credit: AP/Rick Scuteri

PHOENIX — After the hitters staged a dramatic comeback, Starling Marte willed the Mets to a late lead and Carlos Mendoza made all the aggressive and logical moves with his relievers, Edwin Diaz absolutely melted down.

The Mets dropped a heartbreaker to the Diamondbacks, 8-5, Thursday night after Mendoza asked Diaz for a four-out save.

Instead, Diaz walked two batters and gave up a go-ahead grand slam to Corbin Carroll — all with two outs in the bottom of the eighth.

By losing another game that they could have — should have — won, the Mets (69-64) fell to four games behind Atlanta for the last National League wild-card spot. That is their largest deficit in the standings since June 8.

“It hurts,” Brandon Nimmo said. “But there’s nothing we can do about it now.”

Luis Severino said: “It’s a tough one . . . We thought we were going to win.”

And Diaz: “We had it. But we got to keep playing baseball.”

 

For Diaz, it was the second appearance in a row in which he gave up a game-losing home run. The Padres’ Jackson Merrill reached him for a walk-off Sunday.

Diaz blamed a mechanical flaw that caused problems with locating his fastball (consistently outside the zone) and his slider (“floating in the zone,” he said). Carroll caught the latter to seal the game for Arizona (76-57).

“One of those nights where fastball command wasn’t there. He was scattered, couldn’t get ahead of hitters,” Mendoza said.

“Then he hung a slider to a pretty good hitter that got him. It comes down to fastball command, throwing strikes. We didn’t do that today.”

Nimmo said: “Right off the bat, I was pretty sure it was a home run. It’s too bad, but hats off to him. He’s had an amazing series.

“And I know it’s been a rough season for him to start off and he’s rally coming around now and playing like a star player. That was a huge moment for them and a huge comeback for them.”

Carroll’s blast — which landed in the seats, well beyond the glove of rightfielder Tyrone Taylor, who scaled the wall in desperation — was the last twist in a game full of them.

Severino (4 2⁄3 innings) allowed four runs, putting the Mets in a 4-0 hole. Joc Pederson and Carroll took him deep in the third and fourth innings, respectively. Severino got hit in the right foot with a line drive off the bat of Carroll in the third but stayed in the game.

X-rays were negative but he walked with a severe limp after the game.

Arizona lefthander Eduardo Rodriguez, who didn’t allow a baserunner through four innings, gave it all back in the fifth. Harrison Bader crushed a tying home run to cap that rally.

“I thought we did a good job fighting back,” Mendoza said.

The Mets jumped ahead in the sixth when Marte bunted for a single, stole second, advanced to third on a groundout and scored on Pete Alonso’s sacrifice fly. The throw from leftfielder Lourdes Gurriel Jr. seemed to beat Marte, but Marte slid around the tag from catcher Adrian Del Castillo.

That set up Mendoza’s bullpen moves, which looked a lot like how a manager would navigate a postseason contest.

He went to his only lefthander, Danny Young, for a couple of key lefty hitters in the sixth and seventh. He turned to his hottest reliever, Phil Maton, for the eighth. When the potential tying run reached base, he called on Diaz for the final four outs.

Before Diaz, four Mets relievers combined for three hitless innings.

“They did a great job. Everybody did a great job,” Diaz said. “I got to come into the game and get the job done, but I didn’t get my job done today.”

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