PORT ST. LUCIE — The gang was back together again.

After an offseason in which the Mets decided against adding even one new player to the major league roster, the first full-squad workout of spring training arrived Sunday, with introductions unnecessary.

Expectations couldn’t be higher, after an offseason in which the Mets fulfilled their main priority by re-signing Yoenis Cespedes before addressing their bullpen needs by retaining Jerry Blevins and Fernando Salas.

Even with a payroll approaching $160 million, general manager Sandy Alderson said it’s possible the Mets could go higher, if needed, to compete for a World Series title.

“We’re all in here,” Alderson said. “I think it’s a credit to ownership that our payroll is as high as it is now given where we had been as recently as two years ago and where our budget might have been.”

As recently as 2015, the Mets’ payroll was in the $115 million neighborhood.

Manager Terry Collins gathered the players for a morning meeting and issued essentially the same message from the start of camp last year, when the Mets were defending NL champions: Expect success.

Last season, the Mets rallied with a 27-13 finish to the regular season to secure a National League wild-card berth. But their postseason ended with a loss to the Giants in the one-game wild-card playoff.

And now the Mets return with the idea of reclaiming the NL East from the Nationals. Or at the very least another wild-card berth.

“I’m confident we’re going to play in October, I will tell you that,” Collins said.

Cespedes, back on a four-year contract worth $110 million, joked with teammates around the batting cage. Cespedes wore his cap backwards in the cage, spraying pitches to all fields and resisting the temptation to swing too big on the first day.

David Wright played catch — out of sight from reporters — for his first throwing since undergoing surgery in June for a herniated disk in his neck. The Mets captain later indicated he was pleased with the session and will continue to build up arm strength in hopes he will be ready for Opening Day on April 3.

A clubhouse that includes veterans Curtis Granderson, Jay Bruce, Neil Walker, Asdrubal Cabrera and Jose Reyes, in addition to Cespedes and Wright, gives the Mets as much experience as perhaps any team in the National League.

“I’ve never been around this good a mix of veteran guys in the clubhouse, but also the attitude of the younger players to go along with the depth we have,” Wright said.

“I’ll put our character guys up in there against anybody. I’m not sure if that gets you any more wins over the course of a year, but it sure makes it more enjoyable coming to the ballpark and going through spring training with one another when you have the types of great personalities in there that just seem to mesh well together.”

It will take a healthy rotation for the Mets to succeed. And so far, team brass is encouraged what it has seen from Matt Harvey, Jacob deGrom and Steven Matz in their returns from surgery. Zack Wheeler is the wild card, after two years on the sidelines recovering from Tommy John surgery.

Collins wants the Mets to display a “swagger” in their charge toward reaching the postseason for a third straight year.

“What these guys did to persevere through all the tough times, all the adversity, all the injuries, all the doubters, all the things that happen, they better walk around with their heads up,” Collins said. “They better have a little swagger, they better talk winning, they better play like they are going to win, they better act like they are going to win.”