PORT ST. LUCIE, Fla. — While a long-term contract extension with second baseman Neil Walker remains possible, that outlook gets murkier when it comes to the Mets’ stable of young starting pitchers.

Spring training is typically a time for players and teams to engage in extension talks. But on Wednesday, sources indicated that the Mets likely wouldn’t hold discussions with any of their young starting pitchers during camp, with one saying the club was “not optimistic” about talks.

General manager Sandy Alderson has said this offseason that he did not consider extensions talks to be a priority. And it seems that the players have not moved the ball forward, either.

Earlier this month, the Cardinals signed righthander Carlos Martinez to a five-year, $51-million extension even though he was still three years away from reaching free agency. Such deals can provide an opening in contract talks, with players in roughly comparable situations often sending feelers to teams in hopes of gauging the likelihood of extension talks.

It would also be a signal of a players’ willingness to trade away the potential to earn more money elsewhere for the security and stability of an extension.

But Martinez’s deal did nothing to move the needle. According to a source, none of the Mets’ core starting pitchers have given any indication of starting a dialogue. Of course, the Mets aren’t particularly motivated to act, either.

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Injuries have been the most obvious barrier. Matt Harvey, Jacob deGrom, Noah Syndergaard and Steven Matz would be the most logical candidates for extensions. But all except for Syndergaard are coming off surgery. And all aside from Harvey are under team control for at least three more seasons.

Harvey is still under control through next year, though clients of agent Scott Boras typically test the waters of free agency.

Matz and Syndergaard aren’t eligible for free agency until 2022.

“It hasn’t come up and I really haven’t thought about it,” said deGrom, who isn’t a free agent until 2021.

Meanwhile, it’s possible that Walker and the Mets continue talks during the offseason about a multi-year extension.

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Walker, 31, could have been a free agent last season, when he hit .282 with 23 homers, equaling his career-best for a season. Back surgery to repair a herniated disc ended Walker’s season after 113 games.

However, the Mets were pleased with Walker’s recovery, making him a one-year, $17.2-million qualifying offer that he accepted instead of free agency. He took the offer after surveying a market that left him underwhelmed.

After some losing times in his years with the Pirates, Walker wanted no part of a rebuilding project and the Pittsburgh native preferred to stay on the East Coast.

“I wasn’t really excited about the landing spots,” he said.

Nevertheless, even after accepting the offer, Walker said talks of a long-term extension continued late into the offseason. According to sources, there remains a chance that talks pick up again in camp. But there are still complications.

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Mets payroll is already projected to be north of $150 million to begin the season. And sources said that a sticking point for both sides is the $17.2 million that Walker is due this season, and how that figure would impact the structure of a deal.

The sides discussed a three-year deal in the neighborhood of $40 million, a source confirmed, though there had been a regular back-and-forth about a deal.

Though talks aren’t dead, sources said that a deal is not imminent.

Also at issue is a matter of need. The Mets hold an $8.5 million team option on shortstop Asdrubal Cabrera for 2018, Ahmed Rosario is tapped to play shortstop should he stay on his development track.

But by simply making the qualifying offer, the Mets indicated their confidence that Walker’s back issue is resolved. On Wednesday, Walker said he has no physical limitations in camp even as he comes off surgery.

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“There’s no other place that I’d want to be,” he said. “Looking down the road and what’s here, and looking at what’s here and what the potential two, three or four years look like, this is an exciting place to be.”

With David Lennon