BOSTON — Addison Reed arrived at spring training this season believing he would be playing in the 2017 World Series. He said that, to a man, all of his teammates thought the same thing. He experiences the same feeling today, but it’s with the Red Sox, not the Mets.

Only two years removed from a World Series appearance and one year from a postseason trip, the Mets are being dismantled. It’s been happening for nearly a month now. Reed was among the first to go, to Boston on July 31. Most recently, the Mets sent Curtis Granderson to the Dodgers and Rene Rivera to the Cubs.

“There wasn’t a person in the room that didn’t honestly, truly believe we were going to get to the World Series together this year,” Reed said, referring to February in Port St. Lucie, Florida. “It’s a fun thing about baseball, this thing that’s happening now. If you’re not going to stay on that team and do it together, why would you not want to go to a contender? There’s me and five or six other guys from the team that started spring training with the Mets that now have real, real chances of making the playoffs.”

Along with Reed, Granderson and Rivera, Jay Bruce was dealt to the Indians, Neil Walker to the Brewers and Lucas Duda to the Rays in this trading spree. Entering play Saturday, each of those former Mets was on a club within three games of a playoff spot.

“There was no doubt if the Mets stayed healthy, they’d have had a pretty good chance to go the whole way,” Reed said. “Even the year they made the World Series in 2015, there were a ton of injuries and they overcame all of them. And then last year, it was like almost the whole starting lineup was injured again and we still found a way to make it to the wild-card game.

“But you know what? It wasn’t happening this year.”

Reed was acquired by the Mets in a trade with the Diamondbacks in late August 2015. He calls the two months after that — as the Mets reached the postseason, won the pennant and played in the World Series — “the most fun I’ve ever had on a baseball field.”

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He says his current situation feels similar and could have a chance to surpass that.

“It’s pretty scary how close the feeling is here to that,’’ he said. “Especially with these games against the Yankees, it’s like we’ve been down in all of them and there wasn’t any point in those games where you sense you’d lose.”

Reed acknowledges that the Mets are doing the only sensible thing now. Getting something — prospects or salary relief — for a player on an expiring contract and giving playing time to prospects is what teams in the Mets’ shoes do. But he also suggests there could be a longer view to things.

“At the same time, there are guys that they really, really like,’’ he said, “and if they can work things out with them, they can do what the Yankees did with [Aroldis] Chapman: trade you for prospects and then re-sign you.”