The New England Patriots power structure is one where Bill Belichick is essentially in charge of the football operation. His bio on the Patriots website only references coaching, but he is effectively the executive in charge of football operations in that organization.
His No. 2 on the personnel side is director of player personnel, Nick Caserio. He has held that title since 2008, but according to reports, he has since his responsibilities increase since 2013 after Floyd Reese departed the organization. Belichick is in charge, but Caserio handles many of the day-to-day duties of a GM.