The Mets don’t have any plans to demote struggling Edwin Diaz to the minors, or even relegate him to an ever lower-leverage role.

But it sure sounds as if they would if they could.

“At this point, the way we’re set up, we really can’t afford to do that,” Mickey Callaway said as the Mets prepared for a huge three-game set at NL East-leading Atlanta beginning Tuesday. “He’s going to continue to get big outs for us, continue to pitch in big games. And like we did [Saturday night when Seth Lugo pitched the final two innings and Diaz remained in the pen], we’ll pick our spots and do the best we can to win a game every single night.”

Diaz was supposed to be the solution, not the problem. Baseball’s best closer a year ago with 57 saves — tied for the second-most all-time — has been mired in a slump. And it’s only getting worse, with him pitching to a bloated 7.62 ERA over 13 innings since the start of July.

With Lugo limited by a partial tear in his elbow ligament, the Mets are limited in how often they can use him, and Callaway admitted that “it’s difficult, not knowing if he’s going to be available the next day.”

But Callaway acknowledged he’d start giving Lugo higher-leverage looks.

Callaway kept Lugo in for six outs Saturday even after he served up a home run in the eighth inning, and brought Diaz in down a run in the ninth on Sunday. Diaz struck out two but coughed up a two-run home run to seal a 7-4 loss to Washington.

“You always have to be open for adjustments,” Callaway said. “The season’s going to change; guys are going to be effective at times, not effective at times. At this point the sample sizes aren’t that small anymore. I believe that guys have earned a right to do something until they haven’t.”

And Diaz clearly hasn’t, allowing runs in five of his last six appearances. After posting a sterling 1.96 ERA last season to win AL Reliever of the Year, he’s seen it swell to 5.60 this season.

“In the last couple of outings, it’s been my inability to execute my pitches,” Diaz said through an interpreter. “In order for me to have better outings, I just need to execute my pitches.

“The pitches themselves, stuff-wise, are fine. But it’s just about locating the pitches the way that I want them, so that I can have better execution.”

His execution — or lack thereof — has come back to haunt him in the form of the long ball. Diaz has surrendered 11 home runs in 45 innings, including four in his last six appearances. The latest was hanging a 2-1 slider that Victor Robles crushed out to left on Sunday.

“In the series, he’s had trouble hitting the slider, so that’s why I threw it,” said Diaz. “I just didn’t locate it well and that’s why he hit it out. I was just trying to throw it low and away and try to get a ground ball.”

Poor location being punished with homers has been a recurring theme.

“It’s been tough,” Callaway said. “The common denominator in all of his homers is that they’re right down the middle: We didn’t execute a pitch. That’s normally what happens when you give up a home run. But we’re going to work hard and be diligent in getting the ball where we need to. We still have faith in Edwin.”

Diaz has said all the right things, not letting himself get frustrated by either his woes or his changing role.

“I try to have a positive attitude every single time. I’m just trying to get out of the rough stretch I’m in right now,” said Diaz. “If I’m frustrated all the time, it’s just going to get worse. Every single time on the mound, I’m just trying to get better.”