Tom Brady says he knew before the start of last season it would probably be his last year with New England Patriots.
The quarterback joined Tampa Bay Buccaneers earlier this year after 20 years with the Patriots, who he helped to six Super Bowl wins.
"I knew that our time was coming to an end," he told The Howard Stern Show on SiriusXM.
"It was just time to move on," added the 42-year-old.
"I don't know what to say other than that.
"I accomplished everything I could in two decades with an incredible organisation, an incredible group of people, and that will never change.
"No-one can ever take that away from me, no one can ever take those experiences or Super Bowl championships away from us."
Brady is regarded as one of the greatest players of all time having won the Super Bowl more times than any other player - in 2002, 2004, 2005, 2015, 2017 and 2019.
He has made a total of nine Super Bowl appearances and been named the championship game's Most Valuable Player (MVP) four times - both NFL records.
He was named as the league's MVP in 2007, 2010 and 2017, and is second on the all-time list for touchdown passes and passing yards behind New Orleans Saints quarterback Drew Brees.
Brady insisted he had no resentment towards Patriots coach Bill Belichick following his departure from his former club.
He also spoke about not being worried about the impact on his career in joining a Buccaneers side who have not been to the play-offs since 2007.
"I never cared about legacy," he said. "I never once, when I was in high school, said, 'man, I can't wait for what my football legacy looks like'. That's just not me. That's just not my personality."