The Mets' Dominic Smith scores on a ground out by Juan...

The Mets' Dominic Smith scores on a ground out by Juan Lagares during the first inning against the Marlins on Tuesday. Credit: AP/Lynne Sladky

MIAMI — Wedged off first base by rookie Pete Alonso, Dominic Smith — six months Alonso’s junior — is trying to adapt for the sake of his continued presence in the majors.

It’s been working, too, in these opening games of the season. Before getting his first start of the year Tuesday night against the Marlins, Smith has come off the bench several times to play a key role in late-inning rallies as a pinch hitter, then stayed in the game as a defensive replacement for Alonso.

Mickey Callaway has indicated Alonso will get the bulk of the playing time at first, so at least for now this is life for Smith if he is going to be with the Mets.

“He’s been fantastic,” Callaway said. “I have to give credit to the players in that room. Nobody is worried about playing time. You don’t see anybody hanging their head because they’re not starting. They just want to go out there and win games.”

Smith was a part-time player for parts of last season in the majors, but he wasn’t particularly effective at it (nor was he in any other role, for that matter). This year, he has been picking Brandon Nimmo’s brain on how to go about it.

“That’s how he started off his career,” Smith said. “He was a really good pinch hitter.”

Nimmo’s advice: Always be ready. That means starting to warm up as early as the third or fourth inning, hopping into the indoor batting cage throughout the game and trying to anticipate situations in which the manager might plug you in.

That was the same advice former Mets David Wright, Curtis Granderson and Jay Bruce gave Nimmo in recent years, Nimmo said. He’s just paying it forward, and Smith has been receptive.

“How do you get ready for game speed after not being a part of it for six innings, seven innings?” Nimmo said. “I talked with him about what he thinks gets him ready. For me, it’s bumping that [pitching] machine up as high as it’ll go.

“I tried to impart some of that onto him. And tell him to not treat it like an at-bat in-game where you’re trying to feel out a pitcher. You need to research beforehand, know the pitcher before you go in there and be prepared — and once you go in there, that’s an important at-bat.”

And there’s no such thing as getting ready too early.

“It’s better to be ready early than it is to be ambushed,” Nimmo said. “[Smith] likes to soak it up and listen to what the guys like to do, but he’s very confident in his abilities and knows what he does well. I think he’s really done well.”

Smith added: “Stay locked into the game, because you never know. You can come in early and you can come in late. It’s being heady and locked in the game. That’s one of the biggest things I took away from [Nimmo].”

Callaway doesn’t plan to work Alonso too hard. He is the primary first baseman, but the Mets plan to regularly rest their regulars — including second baseman Robinson Cano, who historically plays 150-plus games — so as to not wear them out.

“[Alonso] runs harder than everybody in the major leagues except for maybe Nimmo,” Callaway said with a laugh. “You just watch him play. The kid, if we played him 161 games, he would get tired — 162, 150 games even. He would get tired. So we owe it to our player, we owe it to our team to make sure that we’re taking care of those guys.”

Newsday LogoSUBSCRIBEUnlimited Digital AccessOnly 25¢for 5 months