I have said it before and I'll say it again: Bill Belichick is the most valuable asset in the entire NFL. There is no single person who can influence the shape of a franchise on a week-to-week basis as much as Belichick, and there is no single person or player that would be worth trading for in exchange for Bill.
Robert Kraft would laugh if the Colts offered Andrew Luck in exchange for Belichick. He would hang up if the Ravens offered Ozzie Newsome. He wouldn't answer the phone if the Packers offered Aaron Rodgers.
Earlier in the year, Rotoworld's Pat Daugherty ranked Belichick their top coach in the NFL for the second straight season. There's little to question in that arena; Belichick is not just the best active coach in the league, but is widely considered one of the greatest coaches in the history of football.
Belichick's value is only amplified when it's noted that Rotoworld just ranked Belichick their top general manager in the league for the second straight season.
No other general manager is better able to acquire the depth of talent required to be an annual contender, and no coach is better able to use the players on hand to the best of their ability.
Daugherty notes that while Belichick has flaws (namely his ability to draft wide receivers and cornerbacks), his strengths more than make up for those warts. In fact, Belichick used free agency in 2014 to sign Darrelle Revis, Brandon Browner, and Brandon LaFell to hedge against potential set-backs with Logan Ryan and Aaron Dobson.
The best in the business not only know when to double down, but when to fold, and Belichick certainly knows how mask his shortcomings.
From 2000 through the 2015 season, the Patriots have featured one person, Belichick, at head coach and general manager. The Dolphins have had 9 persons combine at head coach and general manager, the Jets have had 10, and the Bills were the worst with 14 (not including interim coaches).
Belichick just delivered the franchise's fourth Super Bowl trophy in his tenure after the team's sixth trip to the championship under his watch. He's the greatest general manager in the sport. There's a legitimate argument that he's the most impactful person in football for the modern era.