Matt Wisler was on his cell phone when Twitter exploded as news broke that closer Craig Kimbrel was departing Atlanta for San Diego hours before opening day. On the other line: Jace Peterson, who’d just been named the Braves’ starting second baseman.

The two lived together last year in El Paso, teammates on San Diego’s Triple-A team. When they weren’t at the ballpark, Wisler and Peterson would sometimes crack open a beer and brave the hot west Texas nights on their apartment balcony.

They’d talk about life and family. They’d talk about baseball and laugh at Peterson’s frequent shuttling between major- and minor-league clubhouses that year.

They’d also talk about playing together some day in the bigs. Atlanta far from their minds.

That brings the story back to the phone call on the night of Kimbrel’s trade, which sent Wisler to the Braves’ farm system.

“We just talked about how funny it is that we got traded to the same team together,” Wisler said recently. “And how having the opportunity to play together this year would be awesome.”

That opportunity came about two months later, when Atlanta called up Wisler on Friday to take Mike Foltynewicz’s spot in the rotation.

He was facing the then-first-place Mets. First pitch was set for 7:35 p.m. Players arrive at Turner Field around 3 p.m. for night games.

Wisler got there at 12:15 p.m.

“I was sitting around the house just overthinking. So I was like, ‘Screw this, let’s head to the field,’” Wisler said after his debut. “I was nervous as heck the whole day.”

Eventually Wisler’s new teammates started showing up and one guy sat with him for an hour and calmed him down — his old roommate.

“(Peterson) told me, ‘If you start feeling too nervous, just look behind you. Just like last year, I’m right behind you,’” Wisler said. “He said, ‘You’re not out here alone.’ So that really helped.”

It clearly did.

Wisler, 22, looked poised beyond his years, finishing his debut with six hits and one run allowed over eight innings. He joined John Smoltz as the only Atlanta Braves to pitch at least eight innings and allow one run or less in their debuts. And his 88 pitches were the fewest a pitcher has needed to toss eight innings in a debut since 1914.

“I’ve seen him throw some good ones, man,” Peterson said. “To do it in the big leagues, I’d have to say it’s the best (of his career) for sure.”

But entering the bottom of the eighth, Wisler was in line to lose a 1-0 game. Mets starter Jacob deGrom had allowed just two hits over the first seven innings.

Then momentum shifted with one swing. Andrelton Simmons cranked a leadoff double off the left-field wall and Eury Perez sacrificed him to third. Pedro Ciriaco followed with an infield single that kept Simmons at third.

“When (Ciriaco) got on base, you’re thinking, ‘Hey, this could be something,’” Bob Wisler, Matt’s father, said on Monday.

That chased deGrom from the game and brought in Sean Gilmartin, who hadn’t allowed an inherited runner to score all season. His first batter, Peterson, smacked a 3-1 pitch over the head of Gold Glove center fielder Juan Lagares for a two-run double.

“That was the first time that I really breathed a sigh of relief and said, ‘Wow, this is really cool,’” Bob Wisler said.

While Wisler’s dad and many of the 28,853 in attendance roared with approval, Peterson stood atop second base, screaming and smacking his hands before pointing to the dugout.

“He promised to get me a couple runs today,” Wisler said with a smile.

Peterson’s double proved to be the difference and the Braves gave Wisler a 2-1 win and the two former roommates were all smiles in the high-five line after the game.

“(I told him) ‘Congrats, man. Keep working, keep going,’” Peterson said. “’Don’t be satisfied because this game will humble you quick. So keep working and stay on it.’”

Once the postgame interviews ended, Wisler went to the family locker room and greeted about 30 loved ones who traveled from all around the country to see him. He handed his father the ball from the last out he recorded — a strikeout.

“That was a pretty special exchange,” Bob Wisler said.

That night, Matt Wisler got on his cell phone again. On the other line: Nationals pitcher Joe Ross, who’d picked up his second big-league win that night and whom Wisler will face in Washington on Thursday.

Another old friend who’s made good.