PHOENIX -- The setup was precisely what the Mets wanted: a late lead, a bit of momentum, their top reliever on the mound in a game with major National League Wild Card implications.

"You always feel good about your chances when you’ve got your closer, when you’ve got an opportunity to win a game,” manager Carlos Mendoza said.

The reality proved a considerable deal more sour. Entering with a man on base and two outs in the eighth inning on Wednesday, Edwin Díaz threw eight of his first 10 pitches for balls. With the bases loaded, he subsequently hung another slider -- a theme of this road trip -- to Corbin Carroll, who launched it for a go-ahead grand slam.

Not long after, the Diamondbacks polished off their 8-5 win over the Mets at Chase Field to put another dent in New York’s Wild Card chances. The Mets are now four games back of the Braves with 29 to play -- not an insurmountable margin by any stretch, but also not an insignificant one.

"It’s a tough loss today,” Díaz said. “We had it. We had it. We’ve got to keep playing baseball, and at the end of the season, we’ll see where we are.”

On the season, Díaz is responsible for three losses and six blown saves, which have mostly come in two distinct clusters. In June, Díaz blew four saves over a stretch of eight appearances, culminating in a trip to the injured list for a right shoulder impingement. Upon his return, Díaz proved mostly steady until this past Sunday, when he entered a tie game in San Diego and served up a walk-off homer to Jackson Merrill.

Three nights later, Mendoza called on Díaz in the eighth inning in Phoenix. Despite receiving an abbreviated start from Luis Severino, who suffered a bruised right foot on a comebacker earlier in the game, and despite setup man Dedniel Núñez being unavailable due to forearm tightness, the Mets managed to build both a one-run lead and a bridge to Díaz. But it only took a few moments for all of it to crumble.

"[He] threw me a slider, it ended up pretty middle and that was it,” Carroll said.

In his first season back from March 2023 surgery to repair a torn patellar tendon in his right knee, Diaz now has a 4.30 ERA, more than three times as large as the 1.31 mark he posted in his last healthy season in 2022. He has blown twice as many save opportunities in barely half the innings.

"My slider is floating in the zone,” Díaz said, bemoaning a mechanical issue that has him falling toward third base rather than pointing his body in a straight line to home plate.

Díaz is merely part of the issue for a bullpen that has long since lost Brooks Raley and Drew Smith to season-ending elbow surgeries, and that retains only two members from its Opening Day mix. José Buttó, a pleasant midseason surprise, has proven mortal of late. It’s unclear how severe Núñez’s injury is.

If the Mets are going to go on a late run up the standings, they’re going to need to find answers from that unit sooner rather than later.

To be clear: not all is lost. In the immediate aftermath of Wednesday’s loss, both Mendoza and Díaz expressed confidence in the closer’s ability to rebound.

But it is getting late.

The Mets' four-game deficit behind the Braves for the last NL Wild Card spot is their largest since June 8, when they were nine games under .500. While they’ve done well to split six games out West with the Padres and Diamondbacks, both of whom they’re chasing in that Wild Card race, the Mets need to do more than tread water against good teams if they want to pass them.

Losing winnable games on Sunday and Wednesday has put the Mets in a precarious spot.

"We’ve got an uphill battle for sure,” outfielder Brandon Nimmo said. “It seems to me like San Diego and Arizona and Atlanta are really playing good baseball at the right time. In order for us to make our way in, one of those teams is going to have to falter a little bit, and we’re going to have to take advantage of it. None of them are really doing that right now."