PORT ST. LUCIE — This is the first time Lucas Duda will be compared to Corey Kluber, but bear with me a second.

The Mets and Duda are discussing a long-term contract extension, The Post has learned, and some of the elements that are complicating the Indians’ negotiations with Kluber are in play with Duda and the Mets.

Duda described the negotiations as “preliminary stuff and still in the works,” but did not want to go further.

His representative, Dan Horwits, said there have been talks this spring with the Mets, but if nothing is finalized by Opening Day, those negotiations will be tabled until the offseason.

Mets officials did not want to discuss the status of negotiations.

The trouble is properly determining Duda’s value after a breakout season and with him now 29. This is where he has much in common with Kluber.

Like Duda, Kluber was drafted out of college in 2007. Like Duda, he spent a lot of time in the minors and hinted at strong ability, but did not put it all together until last year, when he won the AL Cy Young award.

But college plus the journey means Kluber is older now. He turns 29 in two weeks, and the Indians are weighing how much of a risk it is to commit guaranteed dollars to a starter into his 30s.

Conversely, Cleveland fears that if it goes year to year, his pay in arbitration could become a huge burden to its payroll.

The Indians hope Kluber worries enough about incurring an injury or having his performance regress and never banking any kind of real money that he takes a good deal rather than seeing if there is an exorbitant payday in free agency at age 33.

Duda — college plus journey — turned 29 last month. He broke out with 30 homers last year. He is making $4.2 million in 2015 and he could go year to year and be a free agent after the 2017 season.

But he would be 32 entering 2018. Will an industry only becoming more concerned each season by aging players be ready to do something significant long term with a not particularly athletic player for his, say, ages 32-37 campaigns?

Or would Duda be better served by doing a four- or five-year deal now that could assure he makes at least $50 million-ish in his career?

Of course, that is assuming the watch-the-wallet Mets even would do that. For a while, general manager Sandy Alderson did not want to talk about contracts.

When I asked him if he thought what Duda did last season was aberrational or could be duplicated, he replied, “Good question.”

Translation: There is not a long track record here. The Mets finally picked Duda as their first baseman over Ike Davis early last season. Yet even in a strong year for Duda, he continued in a career-long deficiency against lefties.

Of the 158 players who had at least 125 plate appearances against southpaws, Duda ranked 156th in batting average (.180) and 155th in OPS (.516).

There is value in having a 30-homer platoon player — heck you can argue the Phillies, to their regret, gave $125 million to just such a can’t-hit-lefties-well lumbering first baseman named Ryan Howard.

But the Mets would want to limit the long-term pay if they are playing Michael Cuddyer or John Mayberry Jr. at first vs. lefties.

Duda is trying to attack the shortcoming. He does a drill in which the L-screen is pushed to the extreme right side of the mound and hitting coach Kevin Long, who throws lefty, delivers batting practice.

The concept is to make it as if a big-winged southpaw such as Randy Johnson or Andrew Miller is throwing, forcing Duda to begin with an opened stance and essentially put two eyes on the release point as a way to see the pitch better and also to hang in longer to drive the ball.

“I don’t see why he shouldn’t hit lefties,” Long said.

Duda hit a lefty on Saturday, delivering a triple off Jerry Blevins then homering off Tanner Roark. He began the game hitting .129 with one extra-base hit in 31 at-bats and ended at .171 overall with three extra-base hits.

Duda was slowed earlier in camp by an oblique injury and frequently hitters with pronounced leg kicks take longer to find their swing in spring. Maybe Duda has it now.

In general, the Mets believe Duda’s power is legit.

“I haven’t seen a ball come off the bat like that since a young Cliff Floyd. I haven’t seen exit velocity like that in a long time,” assistant hitting coach Pat Roessler said.

“He’s going to do damage. He has sick pop,” Long added.

Will the belief in Duda’s ability to go long translate into a long-term contract?