PHILADELPHIA — Just as they had three weeks ago, Michael Conforto and Brandon Nimmo switched places.

This time Conforto returned to the major leagues after what the Mets hope was a confidence-building stint with Triple-A Las Vegas. To make room, Nimmo will return to the minors, where he hopes to refine his work in the outfield, specifically in center.

“Definitely, this isn’t the end,” said Nimmo, the former first-round pick who hit .235 with a homer and four RBIs after his promotion on June 25.

Conforto, also a first-round pick, was not expected to remain in the minors for an extended period, and his production only hastened the Mets’ decision. He hit .344 with three homers and 15 RBIs in the hitter-friendly Pacific Coast League.

Now the Mets will learn if Conforto has regained his confidence after experiencing a brilliant April followed by failure.

Conforto, 23, had skipped Triple-A entirely when he was promoted last season and helped propel the Mets to the pennant. But after he hit .365 in the season’s opening month, his average tumbled to .148 from May 1 until his demotion.

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Nimmo will get a chance to play every day, an opportunity that he wasn’t going to get with the Mets’ suddenly crowded outfield.

“I know I have a lot to work on and I know I can still do that in Triple-A,” he said. “But I feel like right now, they really feel like Conforto can help out the team, and I think that he can, too. I hope that he’s healthy and good to go and can help this team, kind of spur them on. A nice winning streak would be good here.”

With Yoenis Cespedes hoping to play more leftfield, Conforto might be forced into playing rightfield, where he would compete for playing time with Curtis Granderson.

A demotion means everyday at-bats for Nimmo, who said his promotion reinforced his belief that he can perform in the majors.

“I think it’s given me some confidence, also helped me realize a dream, and mostly take some stress and pressure off,” he said. “Coming up here and getting a feel for how it is has let me know that it’s the same game, just at a little more consistent pace, but one that I can play at. It’s just given me confidence going back.”