A year ago, Mark Vientos showed up at the Mets’ spring training complex with a Florida-sized chip on his shoulder but no spot on the roster. Last month, with Pete Alonso’s status very much in limbo, Vientos got a phone call telling him to shift his offseason focus to first base, suggesting another February project could be on tap.

And this week? Vientos rolled into Clover Park the happiest Met on record, with Alonso’s return kicking him back to third — his home last season — and the security of knowing he’s now an integral part of baseball’s most dangerous lineup (in the proud estimation of teammate Francisco Alvarez).

“I can agree with that, honestly,” Vientos said.

He’ll need to do more than merely double-down on Alvarez’s boast, though, because Vientos — based on his blistering success over a relatively short period of time — could very well be the slugger the whole thing hinges on.

Last March, Vientos went from being the penciled-in regular DH to booted to Triple-A Syracuse during the final days of spring training, courtesy of the surprise signing of J.D. Martinez. By the end of April, however, Vientos had supplanted struggling buddy Brett Baty as the everyday third baseman. By mid-August, he was the Mets’ No. 2 hitter, the spot reserved for the team’s most lethal bat.

And then there was October, when Vientos showed his flair for the big stage by hitting .327 (18-for-55) with five homers, 14 RBIs and a .998 OPS in 13 games.

Vientos always was confident — demotion after demotion — but in backing up his bravado with that eye-popping production, he took the “Swaggy V” experience to the next level.

The big question: can Vientos stay up in that stratosphere? He’s been doubted plenty before, particularly by the former Billy Eppler-Buck Showalter regime, so silencing the skeptics is nothing new. But often the hardest part about getting to the top is staying there, and Vientos has set the bar awfully high after smashing 27 homers with an .837 OPS in 111 regular-season games.

“I don’t think that’s a fair expectation,” president of baseball operations David Stearns said Thursday. “I think we have to understand that he had a really, really good year last year. He’s worked incredibly hard this offseason because he knows it’s just going to get tougher. The league is going to make adjustments to him and he’s going to have to make adjustments back. So I think what we’re stressing to him is just focus on what you can control, recognize that it doesn’t get easier, but he’s in a really good spot.”

As the starting third baseman for a World Series contender, Vientos wouldn’t argue with that assessment — especially given the situation he’s come from. After frequently being exiled to Syracuse, where he was tasked with improving his defense, Vientos proved over and over that his bat was too big for Triple-A before finally sticking with the Mets last season.

For that reason, neither Stearns nor manager Carlos Mendoza has to school him on handling adversity. Vientos weathered his share of disappointment before last year’s April call-up, and the way he raked upon arrival, it was clear he had no intention of going back down. That mentality is why he showed up this week to work out when only pitchers and catchers were required to be at the facility.

“Goes to show you that he’s not satisfied,” Mendoza said. “Even throughout the offseason, his work was phenomenal — he was getting after it. I saw him in early January and he looked like he was ready to play nine innings. He worked really hard at third base with his defense and physically, he looks really good. The fact that he’s already here, that shows you that he’s on a mission.”

Stearns said the Mets’ goal is to be open and honest with their players when it comes to areas of improvement, and for Vientos, that meant concentrating on his lateral movement. While Stearns mentioned that Vientos isn’t going to have the range of a Matt Chapman (five Gold Gloves), he believes the effort put in is going to yield tangible results, especially after putting first base aside.

Vientos’ glove had been his biggest roadblock to the majors, but he played the position well enough that it never really became part of the conversation. His bat did the talking.

“I love the expectations, I love the pressure,” he said. “I love people rooting for me — or rooting against me. It motivates me to work harder.”

Speaking of hostile environments, Stearns smiled when he brought up Vientos’ tying two-run homer in the ninth inning of NLDS Game 2 at Citizens Bank Park, where Vientos silenced 45,000 people with one mammoth swing, hitting his second homer of the afternoon.

As for how those October heroics translate in predicting Vientos’ numbers this season — FanGraphs’ Steamer projection has him at 32 homers and 92 RBIs — Stearns didn’t claim to have a crystal ball for that.

“I don’t know — other than he’s not scared,” he said. “The moment doesn’t impact him. He’s ready to go and he wants to compete.”

There’s no question Vientos is ready now. It just took last season to convince everyone else, and after what he’s been through, he’ll never stop trying to do exactly that.