PORT ST. LUCIE, Fla. — Little by little, they have flocked here, lured by baseball’s promise of a new beginning.

Many have new scars.

Some are physical, the byproduct of mending muscle and bone.

Some are mental, the invisible price of unmet expectations.

But for these Mets, they are scars all the same, earned during a bruising campaign that they hope will steel their resolve.

Pitchers and catchers officially report Sunday, with position players due on Friday. But in recent days, the Mets’ complex has been bustling with activity, the first wave of what essentially is the same group that went 87-75 and made the playoffs for the second straight year.

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The Mets finished behind the Nationals in the National League East but reached the wild-card game. With the re-signing of Yoenis Cespedes, that crew returns virtually untouched.

“It’s motivation, it’s lessons learned,” said Michael Conforto, the promising outfielder who is coming off a turbulent season.

Conforto, one of the Mets’ early arrivers at camp this season, added: “I know we’re all working hard to get back to where we were two years ago and hopefully finish the thing off.”

Two years ago, the Mets reached the World Series.

Last year, their playoff run consisted of nine agonizing innings against the Giants’ postseason master in residence, Madison Bumgarner.

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The Mets expect better this year, a reasonable goal if they can stay on the field.

“If we wouldn’t have gotten hurt last year, we would have been playing in the World Series,” reliever Addison Reed said. “I’m confident about that.”

‘THEY’RE ALL

FEELING GREAT’

A quick glance around the team’s complex reveals just how much the Mets lost during their slog to October. No group encapsulated those challenges better than the unit that largely defines them: the starting rotation.

On Thursday, two of the Mets’ prized arms, Jacob deGrom and Steven Matz, bounced between practice fields. Both finished the season on a surgeon’s table. Matz had bone spurs removed from his left elbow and deGrom had surgery to calm a nerve issue that had caused pain in his right elbow.

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In throwing sessions with catcher Travis d’Arnaud, both appear recovered from their surgeries.

“It looks like they’re effortlessly throwing over 90 every single time,” said d’Arnaud, offering the kind of glowing reviews that are standard fare in spring training. “They’re spotting up every single time. If they make a mistake, they’re making the adjustment the next pitch, so it’s great.”

Nearby, righthander Zack Wheeler rocked into his familiar delivery, turning his back to the catcher before letting fly with a fastball. He finally looks ready to return. It has been two seasons since he’s set foot on a big-league field, a reminder that while Tommy John surgery may be increasingly common, it still offers zero promises of a smooth rehab.

Soon, Matt Harvey and Noah Syndergaard will join their teammates.

Syndergaard has emerged as the ace of the staff, partly by virtue of getting through last season relatively unscathed. In 183 2⁄3 innings, he went 14-9 with a 2.60 ERA and 218 strikeouts, smothering the rest of the NL with a fastball that rages in triple-digits.

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Syndergaard has taken that unofficial title of ace from Harvey, who is coming off surgery to correct the thoracic outlet syndrome that might explain why he looked like only a shell of himself. But Harvey has been throwing on his own. He’s shown no signs of complications from surgery.

“We have a ton of confidence,” d’Arnaud said. “To have all the guys back, especially the big arms that are back after their injuries. They’re all feeling great. We have all the confidence in the world.”

‘KEEP THEM

ON THE FIELD’

On Friday morning, David Wright stood out from the crowd, the only one to bother with the relative formality of long pants as he ran onto the field for a light workout. Lugging a bat not far behind was Lucas Duda, a notoriously obsessive worker.

A year ago, both had been projected to be major contributors. Neither made a mark, sidetracked by injuries.

So it went all around the Mets’ infield.

Wright underwent surgery in June to repair a herniated disc in his neck, yet another career-altering complication as he learns to play through a chronic back condition. And Duda battled a back ailment of his own, a stress fracture that wiped out his year.

Neil Walker dealt with recurring back pain before it finally became too much. His season ended with surgery for a herniated disc, but the Mets brought him back, extending a qualifying offer that Walker accepted.

Asdrubal Cabrera avoided in-season surgery but wound up on the disabled list for a knee problem.

And just as Wilmer Flores established himself as a dangerous bench bat against lefties, an awkward slide into home plate left him with a fractured hamate bone that cost him much of the season’s final month.

All face varying levels of uncertainty, none more than Wright. But all are expected in spring training healthy.

“Keep them on the field,” manager Terry Collins said. “That’s all we need.”

‘WE’LL GO FAR’

The Mets weren’t necessarily planning on returning almost exactly the same team. Circumstances, however, made it a reality.

The trade market for Jay Bruce flickered and eventually flamed out, leaving the Mets with a glut of lefthanded-hitting corner outfielders. It’s an imperfect scenario that could push the promising Conforto to the minor leagues.

The Mets’ offseason work consisted of signing three major-league free agents: Cespedes, lefty specialist Jerry Blevins and righthanded reliever Fernando Salas. All were on last year’s team.

But the injuries forced the Mets to accumulate depth, much of which they have retained going into 2017. Jose Reyes gives the Mets a versatile veteran with speed. And in the case of Wright, Reyes is needed insurance at third.

If the starting rotation is hit hard with injuries again, the Mets have depth in Seth Lugo and Robert Gsellman. After stabilizing the rotation down the stretch, both drew trade interest. The Mets were not tempted.

“There’s a lot of room for improvement,” general manager Sandy Alderson said on SNY this past week. “I think a lot of it has to do with health.”

Of course, not all the scars were physical. Conforto’s immediate future may be unclear, but the former first-round pick still appears destined to become a force as long as he can move past the worst year of his career.

The same goes for d’Arnaud. The Mets once traded for him, seeing him as the catcher of the future. But for every glint of potential he has shown, he’s also endured struggle. He hit .247 with four homers and lost playing time to Rene Rivera.

But from the earliest days of the offseason, the Mets remained steadfast about sticking with d’Arnaud. Indeed, he has become representative of a team whose fate will hinge on bouncing back.

The Mets are banking on what they have to be enough. And if that sounds overly optimistic, there is at least one projection that backs up that belief. Baseball Prospectus pegs the Mets at 88 wins and first place in the NL East.

“If we stay healthy, we’ll go far,” said Reed, the presumptive fill-in for closer Jeurys Familia, who is expected to be suspended to start the year. “Throughout the course of the season, you’re going to have guys go down. But we have the guys waiting to fill the holes if people get hurt.”