David Stearns hasn’t even taken over the Mets yet and already things are looking up.

On the same day it was learned the former Brewers executive would become their president of baseball operations, the Mets beat the Diamondbacks, 7-4, at Citi Field.

Ronny Mauricio, who has at least given the Mets a bit of a spark since his call-up this month, hit his first major league homer in the fourth inning.

It was one of three home runs hit by the Mets; Pete Alonso added his 44th and Francisco Alvarez hit No. 23.

Brandon Nimmo added three extra-base hits and Jose Butto pitched five strong innings, but the bullpen faltered before Adam Ottavino got Corbin Carroll to hit into an inning-ending double play with the bases loaded in the eighth.

The switch-hitting Mauricio continues to show power from the left side, as his blast to right was another rocket, measured at 112 mph and 440 feet.

“I prepared myself in Triple-A all year and knew I’d be up here at some point,’’ Mauricio said through an interpreter. “I expect a lot of myself and know I’m a good ballplayer. I expected for me to contribute.”

He also was solid again at second base.

Before the game, manager Buck Showalter reiterated that he intends to play Mauricio at multiple positions before the season ends.

After coming up through the minors as a shortstop, the Mets moved Mauricio to different spots this season with Triple-A Syracuse, but he has played only second base since making his MLB debut.

He was there again Tuesday, and he gave the Mets a 2-1 lead with his two-run homer.

Mauricio is about the only young Met who is hitting well.

Brett Baty is in an 0-for-17 slump and Mark Vientos had been hitless in 12 at-bats before his second-inning single.

But Mauricio has produced and on Tuesday, so did many of his more veteran teammates.

Alonso, after 11 games without a homer, has hit five in his last eight games and is tied with Shohei Ohtani for the second-most in the majors, behind only Atlanta’s Matt Olson.

The Mets ran into trouble in the eighth, when Sam Coonrod allowed five of the six batters he faced to reach.

With the bases loaded and one out, the right-hander hit Seby Zavala with a pitch to force in a run.

Coonrod then walked the No. 9 hitter, Geraldo Perdomo, to cut the Mets’ lead to two runs.

Ottavino came in to face the leadoff hitter, Carroll, and got the double play to end the inning.

Right-hander Sean Reid-Foley was placed on the 15-day IL with a right lat strain after he pitched a scoreless inning and struck out three in a loss Monday to Arizona.

Showalter said Reid-Foley mentioned a potential physical issue shortly after the outing.

He appeared in eight games with the Mets after coming back from Tommy John surgery he underwent in May 2022.

Reed Garrett was recalled from Triple-A Syracuse to replace Reid-Foley in the bullpen.

Butto earned his first major league win in front of his wife and son, who were at one of his major league games for the first time.

He struck out a career high seven batters and has pitched well in his last two starts.

DJ Stewart had his first three-hit game since June 6, 2021.

His OPS of 1.244 since Aug. 15 is the fifth-best in the majors.