Ronaldo Nazario was admitted to hospital in Ibiza to be treated for pneumonia, with the former Brazil and Real Madrid great set to be discharged Monday.
Local newspaper Diario de Ibiza said the two-time Ballon d'Or holder and 2002 World Cup Golden Boot winner is in the intensive care unit at the private Policlinica Nuestra Senora del Rosario hospital on the Spanish island, after being taken to a public hospital on the island on Friday evening.
Sources subsequently confirmed the reports to ESPN FC, and later on Sunday the 41-year-old said in a post on his official Twitter account that he is expected to be released shortly.
He tweeted: "Guys, I had a bad case of influenza here in Ibiza, I was hospitalised on Friday, but everything is under control! Tomorrow I get discharged and I go back home! Thank you all for the messages and affection!"
Pessoal, tive um quadro de forte gripe aqui em Ibiza, cheguei a ser internado na sexta-feira, mas já está tudo sob controle! Amanhã recebo alta e volto pra casa! Obrigado a todos pelas mensagens e carinho! 🙏🏼— Ronaldo Nazário (@Ronaldo) August 12, 2018
Ronaldo, who was on holiday when he was taken ill, retired from football in 2011 following a hugely successful career that featured stints at PSV Eindhoven, Barcelona, Inter Milan, AC Milan, Brazilian sides Corinthians and Cruzeiro as well as Real Madrid, where he is a club ambassador.
He won two La Liga titles with Real, the UEFA Cup with Inter and lifted the World Cup in 1994 and 2002 with Brazil, also reaching the tournament's final in 1998.
He picked up the Ballon d'Or award for the best player in the world in 1997 and 2002.
ESPN FC Barcelona correspondent Sam Marsden contributed to this report.