" The ever-combustible Gary Sheffield was overdue for some drama this season, and he finally provided it last night.

The veteran slugger was a late scratch from the lineup, and a high-ranking club source confirmed that Sheffield threatened to leave the team after the Mets rejected his request for a contract extension.

Neither Sheffield nor manager Jerry Manuel did much to clear up the situation before or after last night's 3-2 loss to the Braves at Citi Field, though Sheffield stayed with the team and struck out as the tying run in an eighth-inning pinch hit role.

Sheffield avoided reporters after the game, quickly ducking out of the clubhouse, while Manuel claimed he wasn't aware of Sheffield's extension demand.

Manuel had said before the game that Sheffield had asked for "a day off to kind of clear some thoughts and things."

But Sheffield told reporters shortly after he was scratched -- and before Manuel spoke -- that he did not ask out of the lineup.

"I'm fine," Sheffield said. "It's just the best thing for today. It's just the best thing to let someone else play. I'm 100-percent healthy."

Sheffield is in the final year of his deal and wants to return to the Mets, who are paying him just $400,000 this season while the Tigers -- who released him in spring training -- pick up the remaining $13.6 million.

But the Mets are not interested in an extension because Sheffield will be 41 next season and -- though still a potent hitter -- he has had trouble staying healthy as a position player in the National League.

The timing of Sheffield's request for an extension also was curious because he told The Post earlier this week that he didn't expect to finish the season with the Mets.

The Mets placed Sheffield on revocable waivers last week, but they pulled him back after San Francisco claimed him. By pulling Sheffield back, the Mets are not allowed to trade him.

The Mets' only options now are to place Sheffield on irrevocable waivers or release him to finish the season with a contender, but the team had made neither move as of last night. "