And Manchester City fans paid a classy tribute to their club legend as they chanted his name in the win over Everton.
Aguero, who's City's all-time leading goalscorer, suffered breathing problems during Barcelona's clash against Alaves last month.
He was taken to hospital for tests before being ruled out of action for at least three months to undergo a period of observation.
And reports in Spain say Aguero will announce he'll be hanging up his boots with a press conference possibly scheduled for next week.
Barcelona journalist and streamer Gerard Romero tweeted: "Kun Aguero retires. Heart problems force him to leave football activity.
"A press conference has been scheduled to announce his retirement next week."
Aguero won 15 trophies, including five Premier League titles in his decade at City.
His last-gasp goal against QPR on the final day of the 2011/12 season, which won City their first league title in 44 years will go down in Premier League history.
During City's 3-0 win over Everton, fans chanted 'Sergio, Sergio' in support of their former player.
Aguero's former side made light work of the Toffees at the Etihad Stadium thanks to goals from Raheem Sterling, Rodri and Bernardo Silva.