PORT ST. LUCIE — Want to see the poster boy for change in the Mets’ universe? OK, maybe the second-biggest, after Yoenis Cespedes?

Let’s welcome back The Man Who Would Be Center Fielder.

“I don’t know for sure what’s going to happen,” Juan Lagares said Monday at Tradition Field. “I only know I’m ready 100 percent this year. Last year, I started the season hurt. I feel good this year. Let’s see what happens.”

The Mets will pay Lagares, who turns 27 next month, $2.5 million this season with the expectation that he will start in center field against lefty pitching, with Cespedes sliding over to left field. Against righties, Cespedes will start in center and sophomore Michael Conforto in left, and if the Mets own a lead late, they’ll likely summon Lagares from the bench to take over center field, relocate Cespedes and remove Conforto.

In that role, Lagares can provide considerable bang for his 2.5 million bucks. Next year, though, his salary escalates to $4.5 million, followed by $6.5 million in 2018 and $9 million in 2019. If Cespedes, who can opt out of his contract after this season, sticks around, then Lagares could get boxed into a reserve job while getting paid more and more like a starter. While Curtis Granderson’s contract runs through 2017, creating a potential opening for 2018, a 2 ½-year apprenticeship would be quite a long term for Lagares after he seemingly won the everyday center-field job (and a Gold Glove Award) in 2014.

Quite simply, Lagares finds himself a casualty of higher aspirations, a concept to which no Mets fan would object.

His poor play last season (a terrible .259/.289/.358 slash line in 465 plate appearances), at least partially the result of an ailing right elbow, pushed the Mets to acquire Cespedes from Detroit. An opportunity to re-prove himself in 2016, the same sort of second chance given to homegrown Mets like Ike Davis, Lucas Duda, Daniel Murphy and Ruben Tejada earlier in the Sandy Alderson/Terry Collins reign, seemed on track when the Mets signed Alejandro De Aza to share time, but probably not share a strict platoon, in center.

Then Cespedes accepted his three-year, $75 million contract with an opt-out. Lagares said he was “a little surprised. But I know probably he wanted to come. He did a really good job for us.”

Lagares declined to utilize the “As long as we win” cliché. He wants to play regularly, clearly. He and Collins haven’t talked about the plan for playing time, both men said.

“I always say you have to control what you can control,” Lagares said. “That’s working hard every day and trying to do the job when you get the opportunity.”

He controlled his winter by working out with former Met Jose Reyes in New York for about a month — Reyes’ current legal troubles notwithstanding.

“As we all know, Jose comes to camp in as good a shape as anybody,” said Collins, who described Lagares’ condition as “absolutely fabulous”— after playing in 16 games for Aguilas in the Dominican winter league.

Lagares rested and rehabilitated his arm, communicating consistently with Mets head trainer Ray Ramirez, and he said he’ll be uninhibited in Grapefruit League action.

“If Juan is where he was a couple of years ago, it might work out,” Collins said. “Maybe last year, he said, ‘Look, I’m not going to let this happen again. I’m going to be ready.’ He looks terrific on the field.

“But again: We sit here today and hope that nobody gets hurt. … We know that’s not reality. The reality is somebody’s going to go down, and Juan’s going to be ready. He showed us last year, he got that chance in the World Series and played as good as anybody. So he came into camp. I’m sure he’s saying, ‘Hey, I’m bound and determined to show them I’m still the guy I was a couple of years ago.’ ”

Not long ago, that optimism and Lagares’ contract would have assured him of an everyday spot in the Mets’ lineup. The pace here has picked up considerably, though. Even with his personal future in question, Lagares now stands as a symbol of organizational progress.