Even the threat of another defection to the Nationals hasn’t softened the Mets’ stance on a long-term deal for Yoenis Cespedes.

With a report surfacing Thursday that the NL East rival Nationals have offered Cespedes a five-year deal — which would pair him with Mets postseason star Daniel Murphy — a person familiar with the team’s thinking told Newsday that the Mets’ interest in the slugger remains limited to a three-year deal at most.

The Mets, according to the source, have maintained contact with Cespedes’ agents at Roc Nation Sports. However, the Mets have expressed little desire to change their approach despite mounting public pressure to retain the second-half star.

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The Nationals, according to Fox Sports, submitted a five-year deal to Cespedes’ camp. According to an MLB Network report, the Nationals are believed to have offered a contract in the $100-million range, though structured with deferments.

The Mets, according to a source, have not progressed to the point of making an offer. That stance has been consistent with the team’s aversion to giving out the kind of long-term contract that Cespedes seeks. Instead, the Mets had positioned themselves to perhaps jump in if the price tag fell, a scenario that appears increasingly unlikely.

Cespedes, 30, transformed the Mets’ struggling offense after his acquisition from the Tigers in a blockbuster trade hashed out minutes before the July 31 deadline. He stumbled in the playoffs, but without him, the Mets might not have made them. In 57 regular-season games with the Mets, Cespedes had 17 homers and 44 RBIs. He posted a .287/.337/.604 slash line, far outpacing his career average in each category.

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Cespedes was the final piece the Mets needed to pass the Nationals in the standings on the way to their first division title since 2006 and their first pennant since 2000. But despite the magic of that summer fling, a reunion has long appeared unlikely for the Mets, whose payroll has remained locked in the bottom third of the league after the Bernard Madoff financial scandal.

Internally, part of the Mets’ resistance to a long-term deal stems from questions about whether Cespedes’ production would be sustainable. His career .319 on-base percentage is on the low end for an impact bat. Of lesser concern are his off-field quirks. He preferred not to take batting practice with teammates and often smoked cigarettes in the dugout before games.

The composition of the roster also presents hurdles. With Michael Conforto in left and Curtis Granderson in right, Cespedes would have to play centerfield, his weakest position. The Mets signed Alejandro De Aza to share center with former Gold Glover Juan Lagares, who signed a long-term contract last spring.

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Although the Mets added shortstop Asdrubal Cabrera and traded for second baseman Neil Walker to replace Murphy, they lack the power threat that Cespedes would bring.

Under general manager Mike Rizzo, the Nationals have shown a willingness to shift course. Last year, they gave Max Scherzer a seven-year, $210-million deal despite a crowded rotation. They face a similar situation in their outfield, which features Bryce Harper, Jayson Werth and Ben Revere. So although an obvious landing spot for Cespedes doesn’t exist, the Nationals apparently have emerged as serious suitors.