ALAMEDA, Calif. (AP) - The Oakland Raiders have agreed to a five-year extension to keep guard Gabe Jackson under contract through the 2022 season.

A person familiar with the deal said Friday that it is worth $56 million. The person spoke on condition of anonymity because the deal and its terms have not been announced. NFL Network first reported the deal.

Jackson has been a key part of the Raiders offensive line since being drafted in the third round. He did not allow a sack in 628 pass block snaps last season, according to Pro Football Focus, the best rate for any guard in the league.

Jackson is the second prominent member of Oakland's stellar 2014 draft class to get a lucrative extension this offseason. Second-round quarterback Derek Carr signed a $125 million, five-year deal last week. First-round pass rusher Khalil Mack is under contract through 2018 and will likely be in line for an extension next offseason.