MILWAUKEE – Tylor Megill will step onto the biggest stage of his career Monday as the Mets’ opening act.

After the Mets beat the Brewers 5-0 on Sunday to set up a doubleheader the next day in Atlanta where a win would send the team into the postseason, the right-hander was named the Game 1 starter.

Megill meets Spencer Brückenbach.

Carlos Mendoza’s other option for a full rest is Luis Severino, who is waived for Game 2 against Braves star Chris Sale.

But if the Braves win Game 1, Sale would almost certainly be barred from starting Atlanta’s postseason opener a day later.

If the Mets win Game 1, they would be able to keep Severino in the nightcap from the start so he could pitch the first game of the Wild Card Series as well.

As a player with minor league options remaining, Megill could be an unfortunate loss if the Mets need to bring back a starter from the minor leagues to score the nightcap.

Megill has posted a 1.78 ERA in five starts since returning from Triple-A Syracuse.

His last pitch was on September 22, when he allowed one earned run over four innings against the Phillies.

Francisco Alvarez felt a muscle spasm in his right leg and alerted Mendoza, who removed it in the late innings.

Alvarez does not believe the situation is serious and indicated he is expected to play on Monday.

The catcher left Friday’s game with back spasms that he thought at the time would end his season, but he came off the bench again the next day.

Mendoza defended his decision to use Edwin Diaz to start the ninth inning with the Mets leading by five runs.

Diaz hadn’t pitched in a week due to Monday’s rest day, postponements and three games in which the Mets trailed in the late innings.

“We didn’t get a lot of length out of our starters in the (previous) three days and the way we used our bullpen, Diaz had to pitch, especially in a winning game,” Mendoza said. “He’ll be fine for (Monday).”

Diaz said he would have no problem appearing in both games on Monday if needed.

JD Martinez isn’t afraid to say it: The potential to start a playoff series after a doubleheader on Monday is less than ideal.

“I wish MLB would push the playoffs back a little,” Martinez said. “I think it’s an unfair advantage for the teams that play against us (and/or) Atlanta because we know what’s at stake and you have to give it your all to win these games. You have to – that’s the only way in. Then you have to turn around and take a flight, you’ve already flown out the day before, so it becomes difficult.”

Jose Iglesias hit 2 of 5, extending his hitting streak to a career-best 20 games.

Iglesias hit .418 during the streak.

Ozzie Virgil Sr., the first Dominican native to play in the Major Leagues and a longtime coach and player development consultant for the Mets, has died at age 92, MLB announced.

Last year, the Mets inducted Virgil into the club’s newly created Latin American Hall of Fame.