After playing college football for the Fresno State Bulldogs, he was selected by the Patriots in the first round of the 2005 NFL draft.

As a freshman in 2001, he started all 14 games at left tackle, blocking for quarterback David Carr and allowing only two sacks.

As a junior in 2003, Mankins tore his ACL in preseason practices after a vicious hit from Juan Carrasquillo and missed the season.

[4] Despite playing his entire collegiate career as a tackle, Mankins was moved to left guard by the Patriots, where he immediately stepped into the starting lineup in place of Joe Andruzzi, who departed in free agency.

[6] He scored his first NFL touchdown in the AFC Championship Game against the Indianapolis Colts when he recovered a Laurence Maroney fumble in the end zone.

At the end of the 2009 season, Mankins was selected as a starter to his second Pro Bowl and became just the second guard, after John Hannah, in Patriots history to do so.

Mankins reported to the Patriots and signed his tender on November 2, in advance of the team's Week 9 game against the Cleveland Browns.

[8] He did not have to report until Week 12 in order to be on the roster for the necessary six games to earn his sixth accrued season of free agency credit.

[13] Late in negotiations to complete a new NFL/NFLPA Collective Bargaining Agreement came reports that Mankins and several other players were demanding $10 million apiece or immediate granting of free agency status before they would sign off on settlement of a lawsuit against the NFL as part of a new CBA.

[14] On July 26, 2011, it was announced that Mankins would sign his franchise tender, worth just over $10 million, for the 2011–2012 season, and report to Patriots training camp on time.

He only became aware of how serious the injury was after he tore the MCL in his left knee, during the divisional round playoff game vs the Denver Broncos.

Despite both ACL and MCL tears in separate knees Mankins still went on to play in Super Bowl XLVI vs the New York Giants.

[22] The trade was a move by both the new head coach Lovie Smith and new general manager Jason Licht to fill the void left by Pro Bowl guard Davin Joseph, who was released along with all other members of the offensive line from 2013 season.