ATLANTA -- About four hours before his inaugural at-bat as a big leaguer, Brett Baty spoke at some length about his lack of expectations. He could be here a week. He could be here two decades. All he knew was this:

“I’m here for a reason,” Baty said. “I’ll let it show.”

Four hours later, Baty jogged around the Truist Park infield dirt, having become the fifth Mets player to homer in his first career at-bat (and doing so on his first career swing). His light brown hair peeked out from beneath his helmet as he thrust his index and pinkie fingers into the air, eyes seeking his parents and sister in the stands. Baty’s family, having driven in from Texas the previous night, flashed the bull horns back at him.

In the visiting dugout, another celebration awaited as Baty received hugs and high fives from his brand-new teammates. Jacob deGrom smacked his hand on top of Baty’s helmet, tilting the brim down over his eyes. Baty grinned out from beneath it, in bliss.

“He probably thinks he belongs here now,” starting pitcher Max Scherzer said. “That’s a good thing. That’s what we need.”

By the end of the Mets’ 9-7 win over the Braves, it was abundantly clear that Baty belonged. In addition to joining Mike Jacobs, Kazuo Matsui, Mike Fitzgerald and Benny Ayala as the only Mets to open their careers with a homer in their first at-bat, Baty smoked a 113 mph line drive off left-hander Tyler Matzek, delivering the hardest-hit ball by a Met in a left-on-left matchup since 2016. On the first defensive play in his career, he made a running throw to nab Ronald Acuña Jr. at first.

He finished 1-for-4 and handled all four of his defensive chances without significant issue, in a game the Mets held on to win thanks to Starling Marte’s two homers and Scherzer’s much-needed length despite a 34-minute rain delay.

“I think about not only Brett, but all the people that got some joy out of it,” manager Buck Showalter said.

One day earlier, Triple-A Syracuse manager Kevin Boles had found Baty in the batting cage in Charlotte, N.C., to deliver the news of his promotion. One half of the Mets’ third-base platoon, Eduardo Escobar, was following the other half, Luis Guillorme, to the injured list. The Mets had an imminent need at the position and they wanted Baty to fill it, despite the fact that he had been at Double-A Binghamton just nine days prior.

The promotion completed a rapid rise for Baty, the 12th overall pick in the 2019 Draft and the Mets’ second-ranked prospect, according to MLB Pipeline. As one of the oldest high school players in his Draft class, Baty had always been primed to progress quickly. And so he did, slashing .312/.406/.544 with 19 home runs in 89 games at Binghamton to reach Triple-A earlier this month. Along the way, Baty became more adept at hitting the ball in the air as a means to generate additional power. He acquitted himself at Syracuse with eight hits in six games, tempting Mets officials to promote Baty again despite concerns about his third-base defense.

When they did, Baty’s hitting coach, Joel Chimelis, told him he deserved it and urged him not to worry: baseball is no different in the Majors than it is at Triple-A.

“Regardless of what happens, there is a moment that you kind of step back and take it all in from a baseball fan standpoint and put yourself in their shoes a little bit,” Showalter said. “You do kind of live through it with them and hope that things go well for them.”

Unable to make the first flight out of Charlotte, Baty landed later in the evening and tried to sleep as best he could. When he arrived at Truist Park the following afternoon, he found a gray No. 22 jersey hanging in his locker. One of Baty’s new teammates, Brandon Nimmo, pulled him aside to tell him the Mets trusted him and had his back.

Nimmo also advised Baty to “slow down.” As a former first-round pick himself, Nimmo is one of a small number of people who understand exactly what awaits Baty. Not every day, Nimmo knows, will be as perfect for Baty as Wednesday.

But Wednesday was about as ideal as they come. Following the game, Mets players doused Baty in the shower with a concoction of substances, laughing as they later declined comment on the proceedings. Baty eventually cleaned off the debris, then changed back into his uniform so he could take pictures with about 20-25 family members, friends and ex-coaches who had traveled to see him play.

More than an hour after the game ended, that group was still at Truist Park, forming a ring around Baty as he lounged against the railing of the visiting dugout.

“Just pure joy,” was how Baty described it. “To be able to help this ballclub out in my first at-bat, and then to look up and see my family up there and be able to celebrate it with them? Just pure joy for sure.”