Hired by the team in 2000, Belichick turned to little-used second-year quarterback Brady in 2001, who led the Patriots on an improbable run to the team's first of six Super Bowl championships with the coach at the helm.

"I'm incredibly grateful to have played for the best coach in the history of the NFL," Brady said in an Instagram post.

"We accomplished some amazing things over a long period of time, many of which will be hard to replicate. He worked every day to help us achieve the ultimate goal, in the ultimate team sport.

"And, although we were successful, some of the greatest lessons I learned were in the moments where we faced the most challenging adversities.

"He set the tone for the organization to never falter in the face of adversity, and to do what we could do, and what was in our control, which was to go out and DO OUR JOB.

"I could never have been the player I was without you Coach Belichick. I am forever grateful. And I wish you the best of luck in whatever you choose next."

Julian Edelman, the former Patriots wide receiver who won three championships and took home Super Bowl MVP honors in 2019, posted a humorous montage as a tribute to Belichick.

"Wouldn't change a thing," Edelman captioned the video on social media network X.

Former Patriots offensive coordinator Charlie Weis, who won three championships with Belichick, praised his loyalty.

"In June 2002 right after winning Super Bowl 36, I had a surgery gone bad and almost died," Weis said on X.

"Most head coaches would have taken one look at me and moved on. Not Bill Belichick. He stuck with me personally and professionally.

"Great coach, great man. Patriots/NFL legend! Thank you BB!"

Boston-area sports teams and top athletes from around the country offered their congratulations to Belichick, a likely future Pro Football Hall of Famer who many consider to be the greatest NFL coach of all time.

"Coach Belichick is such a LEGEND!!!!" Los Angeles Lakers star LeBron James said on X, adding a salute emoji.