The move, in essence, would prolong the negotiating period between Mankins and the Patriots, who have been engaged in a rocky contract dispute since before last season.
"I would never say the door is totally shut," he said. "But the way it's looking right now, I don't see it happening. I don't see them trying to keep me, unless it's with the franchise tag."
Mankins was a restricted free agent following the 2009 season, and he and the team couldn't agree on a contract. The six-year veteran eventually signed a reduced tender offer in November and returned for the final nine regular-season games to accrue another season in order to qualify for unrestricted free agency this offseason.
The Associated Press contributed to this report.