Rift Forming Between Sheffield, Mets?

Joel Sherman of the New York Post is reporting that Gary Sheffield and the Mets are at odds about his contract situation. Sherman cites "two sources" who say that Sheffield asked the team for a contract extension and was denied. The sources say he is now threatening to leave the team. The two parties are now in discussions, according to Sherman, and the release of the aging outfielder is "a possibility." Sheffield was pulled from the roster for tonight's game, but Jerry Manuel said he pulled himself "to clear his head."