The Boston Herald reported Wednesday that Mankins' contract money was structured to ease the salary cap hit on the Patriots. The paper didn't say how much the contract was worth and the team hadn't announced the deal publicly yet.
Earlier, Patriots owner Robert Kraft said Mankins would be "signed up soon, hopefully to be a Patriot for life."
"If I have a vote, it will get done," Kraft said about the prospects of signing the star guard to a long-term deal. "But the other side has to want it, too. But it's our desire and has always been our desire."
Mankins, who was one of the plaintiffs in the players' antitrust lawsuit against the NFL that was a feature of the lockout, had signed his franchise tender last month.
He was a holdout last season as a restricted free agent and missed the first seven games of the year. He started the final nine games, then failed to work out a long-term deal and was given the franchise tag designation in February.
When the union decertified just prior to the lockout, Mankins became one of 10 players that attached his name to the antitrust lawsuit filed against the NFL. There had been reports in the final days of the lockout that Mankins and San Diego's Vincent Jackson were holding up an agreement on the new collective bargaining agreement for some type of compensation.
Mankins, who denied the allegations and reported to camp on time this year, was due to make about $10 million for the 2011 season before the sides agreed on a long-term deal.
Selected by New England in the first round with the 32nd overall pick of 2005 draft, Mankins has started all 89 regular-season games and all 10 playoff games he has appeared in with the Patriots. He was selected to the Pro Bowl in 2007, 2009 and 2010.