LOS ANGELES — The “running” joke on Brandon Nimmo’s home-run trot — if you could call it that — is he never gets to high-five first-base coach Ruben Amaro Jr.

Nimmo is usually sprinting from the batter’s box, so by the time he realizes the ball has cleared the fence, he has already rounded first base.

“Ruben always gives me crud about not being able to slap his hand,” said Nimmo, whose pinch-hit, three-run homer in the ninth inning at Dodger Stadium on Monday was his latest impressive jolt.

In this lost Mets season, Nimmo’s development has been the biggest takeaway, at least among the team’s everyday players. He took a .267/.389/.504 slash line with 16 homers and 43 RBIs into Tuesday night’s game against the Dodgers and had justified the front office’s decision not to trade him last winter, when his name had surfaced as potential trade bait in deals with the Pirates that might have netted Andrew McCutchen or Josh Harrison.

Nimmo’s development might serve as a blueprint for what the Mets need to receive from others in 2019 if they plan to contend for the postseason.

Manager Mickey Callaway cited the season Max Muncy is having for the Dodgers as an example of a player emerging from nowhere and helping a team contend. Muncy entered Tuesday with a .963 OPS after two underwhelming seasons to begin his major league career.

“To get where you want to get some guys have to step up,” Callaway said. “I think you see that in teams that maybe have great seasons, so I think that is always going to be important for guys to step up and maybe blossom a little bit earlier or blossom earlier than you thought they could.”

Substitute for Nimmo names such as Amed Rosario, Jeff McNeil, Juan Lagares and possibly even Travis d’Arnaud, and team officials can see a path to improvement from within.

Regarding the oft-injured d’Arnaud, who is under club control for another season but also a potential non-tender candidate, a club official said: “He’s going to stay healthy one of these seasons.”

The same could also be said for Lagares, who is likely to remain with the Mets based on the fact he is owed $9 million next season in the final year of his contract.

But the most intriguing pieces for potential internal growth are Rosario and McNeil, who have given the Mets a strong middle-infield combination over the last month-plus.

Rosario entered Tuesday hitting .333 with three homers over his previous 22 games and has looked comfortable atop the batting order.

The rookie McNeil has exceeded just about all expectations, with an .855 OPS over his initial six weeks in the major leagues. So a significant question facing the new general manager hire might be trying to decipher whether McNeil is real or if the Mets need to add a second baseman in the offseason. But the Mets also realize there is room for the 26-year-old McNeil to grow.

“Those are two potential candidates of the things we are talking about,” Callaway said, referring to Rosario and McNeil. “They both have the ability to do more than they are even doing now. I think Rosie has one of the highest ceilings in all the major leagues from what we see.

“I think Jeff McNeil can continue to improve every day, especially on defense and at turning two, which I think he’s done a great job at. As he gets more and more comfortable in the major leagues maybe some of that power shows up and he can maybe hit 15 to 20 [homers] for you.”