The New England Patriots legend made the shock announcement on Twitter at 5:19pm (BST) on April 1.
“I’m retiring. In my spare time, I’ll be tweeting #LFG,” Tom Brady wrote on his verified Twitter account, which was registered last month.
The revelation, which comes off the back of the Patriots’ 2019 Super Bowl success, has sent shockwaves across the globe.
However, the timing of Brady’s announcement might be a tell-tale sign he is playing a practical joke.
April 1 is, of course, April Fool’s Day and that often sparks jokers from around the world into action.
And Brady might just be jumping on the bandwagon – especially if he’s on the west coast of America, which is eight hours behind the UK.
That would mean Brady tweeted his stunning retirement announcement at 9:19am.
The so-called deadline for April Fool’s Day jokes is 12pm, meaning Brady would be in the allowed timeframe.
Brady’s announcement did not go down well with Patriots and NFL fans on Twitter, many of whom saw right through it.
“My GOAT also please do not do that to me again my heart didn’t like it,” wrote one.
“I wish it was April 2nd,” quipped another, followed by a series of crying emojis.
A third added “April’s Fools jokes now.” after seeing the tweet in question.
One Twitter user thought recently-retired Rob Gronkowski may be behind the post.
“That’s a fake blue check mark, this is Gronk,” they wrote.
Brady, who was drafted by the Patriots way back in 2000, has won six Super Bowl rings.
His performances have earned him there NFL Most Valuable Players awards.
Brady has also featured in the Pro Bowl 14 times over the course of his career.