NEW YORK — Luisangel Acuña heard from his star brother almost every day during his rise through the minor leagues.

Keep working hard. You looked good tonight. Stay disciplined.

The kernels of advice and encouragement have helped Acuña push through a career that started in 2019 with the Texas Rangers, where he reached Double-A and was a Fall League All-Star in 2022, then jumped into overdrive. From the moment he signed, expectations had come from that last name, which only mounted when the Rangers traded Acuña to the New York Mets last summer for Max Scherzer. But having Ronald Acuña Jr., an NL MVP and four-time All-Star by age 25, as an older brother became fuel.

“That’s pride, inspiration,” Luisangel said recently. “It feeds my desire to work. He’s at the peak. I think that’s the best thing a baseball player in the minor leagues can have, a brother in the major leagues and one who is a superstar. That’s motivation.”

The brotherly advice instilled Luisangel Acuña with confidence he needed after he unexpectedly joined the Mets two weeks ago in the middle of a heated playoff race. The younger Acuña has flourished as the injured Francisco Lindor‘s replacement at shortstop: He’s batting .379 with three home runs and a 1.228 OPS in nine major league games while impressing his peers with his demeanor in the high-stakes contests.

“He’s just calm, poised,” Mets manager Carlos Mendoza said. “It’s just like he belongs in the big leagues.”

Acuña has helped the Mets remain two games ahead of his brother’s Atlanta Braves for the final NL wild-card spot, and for the next three nights, the brothers will be in opposite dugouts at Truist Park for a series that could decide their clubs’ postseason fates. Ronald, out for the season with a torn ACL, traveled to Atlanta to watch his little brother play at the major league level for the first time.

If all had gone according to plan for the Mets, Acuña would not be on the trip.

The plan wasn’t for him to make his major league debut two Saturdays ago during a pivotal road series against the first-place Philadelphia Phillies. The 5-foot-8 Acuña was expected to spend the season with Triple-A Syracuse, where he was batting .258 with seven home runs and a .654 OPS. Still just 22, he was not beating down the door to join a veteran playoff-caliber club, and that was OK.

But as magical as the Mets’ in-season turnaround has been, a reversal that launched the club from 11 games under .500 to 18 games over in less than four months, they have not been immune to injuries. Two in the past month left them short in the middle infield. First, second baseman Jeff McNeil was lost for the remainder of the season with a broken left wrist. Less than a week later, a much bigger blow: Lindor left a game on Sept. 13 with a lower back injury.

Acuña received the call that night, and the next afternoon, he was in the Mets’ lineup in Philadelphia, batting ninth and playing shortstop. He went 2-for-4, recording his first career hit in his second plate appearance. The Mets lost that day and the next before going 6-1 during a crucial homestand, culminating with a series win against the Phillies.

Acuña started six of those games at Citi Field. He recorded hits in five of them. In his first home game, he bounced back from an early run-costing error with three hits, including an RBI double and his first career home run, in a 10-1 rout of the Washington Nationals. He homered again the next night and off All-Star Ranger Suárez on Saturday in a 6-3 win over the Phillies with “Hakuna Matata” — a play on his last name — as his walk-up song.

“That’s sort of the major league start anyone would dream of, right?” Mets president of baseball operations David Stearns said last Friday.

In the Mets’ dream scenario, Lindor is back at shortstop Tuesday and Acuña, who has extensive professional experience at second base and in center field, is moved around the diamond. But that appears unlikely.

On Sunday, Lindor indicated he might not return to play in the regular season, which means he might not return at all if the Mets miss out on the postseason. Lindor, who was considered Shohei Ohtani‘s strongest challenger for NL MVP before the injury, said he expects to play in pain if he does return.

Lindor suffered the injury Sept. 13 in Philadelphia, which forced him to exit the game in the seventh inning. He has since played just one inning. The Mets are 6-3 during that stretch.

“I’m super happy,” Lindor said of the team’s play without him. “I knew that they could do it. I’ve believed in the team since Day One. I believe in what Stearns, Mendy, and the whole front office did from Day One. We have a really good team.”

Acuña has been part of it for less than two weeks, producing at a level unexpected after his struggles in Triple A. Acuña said regularly playing in cold weather for the first time was a factor in his struggles earlier in the year. He credited Syracuse bench coach JP Arencibia for suggesting a mechanical adjustment at the plate in late April — raising his hands instead of having them low like his brother — that produced better contact and improved his ability to hit the ball in the air with power. But plate discipline remained a flaw — he compiled just 32 walks in 587 plate appearances in Syracuse, good for a career-low 5.5% walk rate — and the results remained underwhelming.

“I think it’s always tough to predict that someone is going to perform even better at the major league level than they performed at the minor level,” Stearns said. “I think what we had confidence in was the pulse and that the moment wasn’t going to be too big for him. He’s not going to get nervous. He’s excited to be here, and he believes he can perform in this environment. And, clearly, he has.”

This week, Acuña will play the most important games of his career with a familiar face across the way. At some point, the brothers from Venezuela plan on swapping jerseys. It’ll make for a memorable moment. Between the lines, little brother, equipped with his brother’s wisdom, will look to create a few more.

“He always told me it’s the same game,” Acuña said. “Just do what I know.”