NEW YORK -- Mets manager Buck Showalter was wondering if left-hander David Peterson was going to make Monday’s start against the Marlins. After all, Peterson’s wife is close to giving birth to a boy.

Showalter had a backup plan if Peterson was unable to make the start. But Peterson arrived in the locker room ready to throw.

“Once I’m here, it’s all about the game,” Peterson said. “I have a phone in the training room in case something happens.

“I don’t think we are on the verge of having to dart out of here. It was good to come in, focus on the game, focus on getting a series win.”

Peterson found time to pitch one of his best games of the season, helping the Mets blank the Marlins, 6-0, for their third win of the four-game series.

At first, Peterson was living dangerously. The Marlins pushed runners into scoring position in each of the first three innings, but Peterson stranded six runners across those innings. Of the 24 hitters he faced, Peterson threw only seven first-pitch strikes. But he ended up throwing 5 1/3 innings.

“Having the defense behind me is awesome and it gives me more confidence to go after guys,” Peterson said.

Said Showalter, “He had all of his pitches available to him. You could tell he was in a good, aggressive, attack mode. I would have loved to see him get through the sixth.”

Peterson had help along the way. Adam Ottavino, Drew Smith and Yoan López pitched the final 3 2/3 innings, allowing just one hit and maintaining the scoreless game. It was the Mets’ NL-leading 11th shutout of the season, an impressive feat considering aces Jacob deGrom and Max Scherzer haven’t been on the active roster for most of the season.

“It’s just guys stepping up and really taking advantage of their opportunities,” Brandon Nimmo said. “I’m so proud of Petey today. All you can do is learn from your mistakes, and he has definitely done that. This game is really hard to make adjustments on the fly and to be able to execute them into games. I’m really proud of him doing that. This pitching staff has done a great job of keeping us in ballgames.”

Showalter said teams must be seven to nine starters deep in order to survive the season.

“[There is] a lot of protection that has to go into it,” he said. “There is a lot of data that tells you where the potential breakdowns are, so you would be crazy not to pay attention to it.”

The Mets were able to cash in on Marlins left-hander Trevor Rogers, who pitched five innings and allowed four runs (three earned). New York’s biggest inning came in the fourth, and it didn’t have to hit a home run to extend the lead. J.D. Davis scored on a sacrifice fly by Eduardo Escobar, followed by Jeff McNeil scoring on a wild pitch thrown by Rogers to the next batter.

“We played baseball today,” Showalter said. “We cashed in on the opportunities we had and took what was there.”