The critical conversation took place before negotiations truly heated up. It involved Mets general manager Sandy Alderson and Brodie Van Wagenen, the agent for prized slugger Yoenis Cespedes.

Alderson asked Van Wagenen about his client’s desire for a reunion. When the answer came back in the affirmative, Van Wagenen responded with a follow-up: “Are you in it to win it?”

Alderson, too, offered a simple “yes.” From there, it would be only a few more days until the sides hammered out an unexpected agreement that brought Cespedes back to Flushing.

ColumnLennon: Mets fans have reasons to be excitedColumnLennon: Mets have made a loud statement

“It was the right time to get the deal done,” Mets chief operating officer Jeff Wilpon said Wednesday, one day after the Mets officially announced the three-year, $75-million deal.

The deal, hashed out late Friday night, proved to be a testament to patience and the willingness to compromise.

Cespedes, 30, was expected to fetch a payday more in line with the six-year, $132.75-million deal that fellow free-agent outfielder Justin Upton landed with the Tigers. That belief apparently also had been shared by the National League champions, who held firm on their desire to limit their guarantee to no more than three years.

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But both sides remained in contact. The market evolved. And last week, when he checked with Van Wagenen, Alderson sensed what he called “a gradual merger of interests over a period of time.”

The change came after several public statements through the course of the winter that expressed the Mets’ belief that Cespedes would remain out of their price range. That stance enraged a fan base long critical of the team’s budget-conscious spending, especially with the Mets positioned to contend once more after coming off a charmed season.

“We had to be realistic about where things were,” Alderson said during a conference call yesterday. “It was hard to read into the market because of how Brodie described it, the shifts and so forth that were taking place.”

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Wilpon stopped short of acknowledging that fan pressure played a factor. He also disputed the notion that the Nationals’ reported interest in signing Cespedes had spurred the Mets into action.

However, Alderson said “we understood the magnitude of this issue with the media and our fans,” many of whom were outspoken in their desire to retain Cespedes, who slugged 17 homers after his July 31 arrival via a trade from the Tigers.

Wilpon said the signing proved that the Mets have become a “destination” for players.

“Both sides remained committed to keeping an open mind on creative deal structures,” said Van Wagenen, the head of baseball at CAA/Roc Nation Sports, who credited Wilpon for pushing the deal across the finish line. “Clearly, the player had a desire to be here.”

That creativity proved crucial in the deal’s coming together quickly. Van Wagenen said Alderson showed a “rare” willingness to discuss various concessions that would make a three-year deal possible, even early in the process. Those talks manifested themselves in a frontloaded contract and opt-out clause that made the deal possible.

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Cespedes will make $27.5 million in 2016, of which $10 million will be paid as a signing bonus in the next 30 days, a source confirmed. It makes Cespedes one of baseball’s highest-paid outfielders by average annual value.

The opt-out clause after this season gives Cespedes the option to test the free-agent class next winter, which features a less competitive class of outfielders.

Even if Cespedes opts out, the Mets would be allowed to make a qualifying offer, which makes it possible to receive a draft pick as compensation.

Van Wagenen said he discussed deals from one year to six years with other teams, though he did not disclose specifics.

It remains unclear whether Cespedes actually left significant money on the table out of his desire to stay with the Mets. According to reports from Jon Heyman of the MLB Network and Peter Gammons, the Nationals offered a five-year, $110-million deal. But because of deferments, the actual value of the offer was closer to the $75-million range that the Mets offered. The Orioles reportedly also made a five-year offer,

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Regardless of the circumstances, by bringing back Cespedes the Mets have solidified a lineup that is expected to complement what is arguably the best rotation in baseball. Payroll hovers around $140 million, territory not seen since before the Bernie Madoff financial scandal slammed the franchise.

Said Alderson: “It’s a clear acknowledgment that the present is important to us.”

With David Lennon