In his first season with the team, the Buccaneers finished 2-14 and will have the No. 1 pick in the 2015 draft. The Patriots, meanwhile, finished 12-4 and will play the Baltimore Ravens in the playoffs on Saturday.
Mankins said he recognized the financial reality of the situation, but he was unhappy the trade came so close to the start of the season.
"Looking back on it now, especially in my case, the timing of it was very disappointing," Mankins said. "If it happened during free agency, that would have been a lot different.
"But the timing of how I left was the hardest part."
Mankins has taken on a leadership role with the offensive line in Tampa Bay, and head coach Lovie Smith said Mankins will be a captain next season.
"I picture him going forward as one of our leaders," Smith said. "When he talks, everyone listens. As rewarding as what he accomplished in New England has been, to help Tampa Bay become the up-and-coming franchise we believe it can be will be just as valuable for him."
Tampa Bay finished tied for No. 29 in sacks allowed, No. 29 in yards gained and No. 30 in points this season.
- Paul Palladino