Gallery was drafted second overall by the Raiders in 2004. The six-foot-seven, 320-pound lineman played in 104 games over his eight-year NFL career.
Gallery left Oakland in March of 2011 when he and Al Davis agreed to part ways in the aftermath of Tom Cable's dismissal.
REWIND: Adios, Gallery
He then signed with the Seahawks for the 2011 season, and joined the Patriots as a free agent in March of this year.
Gallery, 32, was competing for a starting spot on New England's offensive line.