By Jon Heyman

The Mets will announce shortly after the season that general manager Omar Minaya and manager Jerry Manuel won’t be returning in their roles, sources say. The announcements are likely to be made before the playoffs begin Wednesday. The changes will not come as a surprise, as they have been widely assumed for a few weeks now.

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It isn’t expected that either replacement will be named immediately. There’s no evidence the Mets have begun contacting GM candidates. The new GM is expected to have a big say in the hiring of a new manager, so the managerial position will remain vacant for a period, as well.

Minaya is believed to have an option to leave the organization once he is removed as GM, but a couple people close to Minaya said he may consider another position within the organization if it suits him, though others suggest he may choose to leave. Minaya’s background and greatest strength is in scouting. The team will be responsible to pay the final two years of a contract that pays him at least $1 million annually. Minaya is beloved by his co-workers, and several people hope he stays, but that is no certainty.

The Mets hold an option on Manuel’s contract that won’t be renewed. He is also well-liked in the organization. Both Minaya and Manuel had early successes in their tenures.

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Mets higherups are concerned about ticket sales and seem to be considering high-profile people for both jobs.

The Mets are planning to go outside the organization for the GM position and are thought to be considering several people, including former Diamondbacks GM Josh Byrnes, White Sox assistant GM Rick Hahn and former A’s GM Sandy Alderson. Rangers GM Jon Daniels, a Bayside, Queens product, could be an intriguing option as he has an “out’’ in his Texas contract, but the new Rangers ownership group led by Chuck Greenberg has made it clear they wants to retain him. Respected assistant GM John Ricco is expected to stay in his current role, but is said by people to fully understand the intention to go outside the organization for the GM position following a second straight losing season. The Mets will improve from their 70-92 mark a year ago, but not enough to satisfy the club-owning Wilpons. They have missed the playoffs four straight seasons.

Wally Backman has been mentioned prominently as a possible in-house managerial candidate, but there will be others. Some both inside and outside the organization believe it’s a leap to think someone should be promoted from the Class-A Brooklyn Cyclones to manage the Mets, but he is liked by some with power in the organization, is credited for a very good job in Brooklyn and fits the profile of a “high energy’’ manager they will seek. Bobby Valentine is expected to be discussed, and while he succeeded in his first stint it isn’t yet known whether either party desires to go for a second go-round. Valentine could also be a candidate elsewhere, including Seattle.

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