Josh Naylor re-signs with Mariners to five-year deal as Mets lose potential Pete Alonso fallback option

One of the more attractive Plan Bs if the Mets don’t re-sign Pete Alonso is already off the market.

First baseman Josh Naylor agreed to a five-year contract to return to the Mariners. The Post’s Jon Heyman confirmed this Sunday night, during the MLB’s first major signing of the offseason. Financial terms have not yet been announced.

Naylor, 28, was acquired by Seattle from the Diamondbacks at the trade deadline and had an .831 OPS with nine home runs and 19 steals in 54 games while hitting .299.

It was part of a fantastic all-around year with 20 home runs and 92 RBIs

Naylor helped the Mariners win the AL West and make a run to Game 7 of the ALCS before falling to the Blue Jays. He went 10-for-24 in the series and hit .340/392/.574 in the playoffs with three home runs and five RBIs.

Naylor gives the Mariners a second big bat around lanky catcher Cal Raleigh as they look to build on their success. Naylor also played for the Guardians and Padres.

The former All-Star was thought to be a strong fallback option for the Mets if they were unable to bring Alonso back in free agency.

The Mets’ all-time home run leader, who is no longer tied to the qualifying offer, had a strong 2025 even as the team collapsed and failed to make the postseason.

Alonso won his first Silver Slugger while hitting .272/.347/.524 with 38 home runs, 41 doubles and 126 RBIs.

Heyman predicted that five years, for $164 million, would make sense for Alonso.

If the Mets can’t get that done, Cody Bellinger remains a possible option if he doesn’t return to the Yankees, as does Japanese infielder Munetaka Murakami.