The Mets made what they perceived as a last-ditch effort to sign Pete Alonso by offering him a three-year contract in the $68 million-$70 million range, and when that was rejected, began their pivot away from their slugging first baseman, The Post has learned.

The first step was to add another bat by re-signing Jesse Winker for one year at $7.5 million.

They now will try to bolster their pen by playing at the top of the relief market, and the No. 1 asset available is lefty Tanner Scott.

The Mets did not send out a statement that the Alonso Era was done. But they have come to believe — without some unexpected late reversal — that it is.

The Alonso camp had made the Mets a three-year proposal with average annual values way beyond where the franchise was comfortable going.

So the Mets countered with an offer that would be worth more than the three years at $60 million at which Christian Walker signed with the Astros this offseason. Walker will play at 34 next season, Alonso at 30.

This bid included opt outs for Alonso that if he rejected and stayed would have carried the offer at least slightly beyond $70 million, a source saod.

But Alonso was looking for more and the Mets came to believe the gap was going to just be too great to close.

Thus, they signed Winker to a deal that could rise to $9 million if he hits all of his bonuses.

The current plan is to shift Mark Vientos to first base and have Luisangel Acuña, Brett Baty and Ronny Mauricio vie for third base.

The Mets will hope Juan Soto, in particular, and a full season of Winker help offset any loss of Alonso’s might.

And they will try to be stronger elsewhere by capitalizing on a free agent relief market that has mainly not moved.

Besides Scott, Carlos Estevez, Kenley Jansen, David Robertson and Kirby Yates remain among the many still available.

The Mets had informed Alonso’s camp in recent days that time was short to make an agreement because the organization did not want to miss out on other opportunities waiting for the slugger to decide if he would accept the team’s offer.

The Mets, with Billy Eppler then as general manager, made a seven-year, $158 million extension offer to Alonso in June 2023 that would have covered the final year of club control and six free-agent seasons. He rejected that bid and subsequently made $20.5 million in his final arbitration season.

Since then, David Stearns took over baseball operations for the Mets. Stearns does not like to give weighty contracts to players in their 30s, especially non-athletic corner players, and he emphasizes defense.

That led to the Mets changing their view on how to proceed with Alonso, a fan favorite who sits third all-time in franchise homers with 226 — and well within striking distance of Darryl Strawberry’s mark of 252.

Alonso now is very likely to end up elsewhere.

The Blue Jays, who have had difficulty recruiting big-name players to Canada and have a huge hunger to reverse that, are seen as a strong contender now in the Alonso sweepstakes.

If Toronto signs Alonso, they can pair him with Vladimir Guerrero Jr., who could move to his original third base and/or flip-flop first and DH at-bats with Alonso.

Alonso finished this past year with 34 homers and 88 RBIs, career lows for a full season, as well as a career-worst .788 OPS.

He rebounded well in the playoffs, though, with a .999 OPS and four homers in 13 games, including his go-ahead, three-run homer against Milwaukee in the top of the ninth off closer Devin Williams that helped the Mets advance to the NLDS.

But he’s so far been left out in the flurry of transactions among first basemen this offseason, which includes Paul Goldschmidt, Jake Burger, Nathaniel Lowe, Josh Naylor, Carlos Santana and Walker all landing in new spots, as well as Detroit taking itself out of the first-base market when they signed Gleyber Torres to play second and moved Colt Keith to first.

So for now, the Mets are moving forward as if one of the best power hitters in their history is going to play elsewhere in 2025.

They will take their chances with a revamped lineup that includes the addition of Soto on a 15-year, $765 million contract, as well as a rotation that’s retained Sean Manaea for three years and $75 million, as well as added Frankie Montas to make up for the loss of Luis Severino.

It’s part of a significant makeover of a roster that made a surprise run to the NLCS last season, where the Mets lost to the World Series-winning Dodgers in six games.