PORT ST. LUCIE, Fla. — Back in October 2015, everything looked so rosy for the Mets and their pitching prodigies.

With two impressive rookies in a dazzling young rotation that featured four power arms, the team had already reached the World Series and the future was full of possibility.

Jacob deGrom, Matt Harvey, Noah Syndergaard and Steven Matz — with Zack Wheeler working his way back from Tommy John surgery. None older than 27 at the time, each with immediate big league success under his belt.

"When I saw them back in '15, I was very envious. I was very jealous. You know that's a special group," said new Mets pitching coach Dave Eiland, who held the same position with the Kansas City Royals squad that beat New York in the World Series that year.

And then they kept getting hurt.

Fast forward to Wednesday, when New York opened spring training 2018 with its first scheduled workout for pitchers and catchers. Still, the Mets have never had that entire quintet in the rotation at the same time.

With an embattled Harvey eligible for free agency after the season, this could be their last chance.

"There's nobody from a medical standpoint that we're holding back," Eiland said. "Right now it's all systems go."

One day into camp — so far, so good.

But there's a long time before opening day March 29.

When Syndergaard tore a lat muscle on April 30 last year and slugger Yoenis Cespedes missed half the season with hamstring problems, New York fell apart and finished 70-92.

The five projected members of the rotation combined for only 86 starts, and a couple of those were very brief outings by Syndergaard after he returned in late September. Harvey, Matz and Wheeler all went down with long-term injuries again.

Maybe a bigger concern: Even when those three did pitch, they were mostly ineffective.

Coming off surgery for thoracic outlet syndrome, Harvey developed shoulder discomfort in 2017. He seemed to lose his stuff — and his confidence — while going 5-7 with a career-worst 6.70 ERA during his second consecutive miserable season.

"Mechanically, I'll be honest with you, it looks to me like he got in some bad habits. Simply because he had some injuries," Eiland said. "It looks to me like he was doing something with his lower half to help his upper half, which is his arm."

"He's aware of it. We've talked about it. We've looked at film. His last couple of sides — Matt was here early, so we were able to get some sides in here in the past week, and he's gotten back on track a little bit," Eiland added. "He's healthy. He's done his work this winter. He's in good shape, physically and mentally."

Wheeler finally made it back last year after missing two full seasons following Tommy John surgery, but he lost his last five decisions and didn't pitch after July 22 because of a stress reaction in his right arm.

Desperate to get healthy, Wheeler chose to take medicine designed to strengthen bones, subjecting himself to an injection in his stomach every day for six months.

"You have to prepare guys to be better than they have been in the past," said new manager Mickey Callaway, a successful pitching coach with Cleveland. "That's our goal."