Tottenham midfielder Sandro is expected to be out of action for three months after undergoing knee surgery on Friday.
Sandro, 22, returned to London after suffering the injury on international duty with Brazil on Monday and will miss the first two months of the new season.
Sandro was sent for a scan after complaining of pains in both his calves and his knee in training during Brazil's Copa America campaign in Argentina.
Results showed that the midfielder had ruptured the meniscus in his left knee - an injury which requires surgery and usually takes around a month to heal - but specialists have now delivered a worse prognosis for Spurs.
A statement on the club's official website read: "Following consultation with an independent knee specialist, Sandro underwent surgery on his left knee in London.
"Sandro withdrew from Brazil's Copa America campaign on Tuesday due to injury with scans confirming he had torn his lateral meniscus, as well as suffering a calf strain.
"The specialist has advised a three-month rehabilitation period before a return to full training.''
Sandro has become a popular figure at White Hart Lane since his move to the club in August 2010.
The Brazilian, who signed from Internacional for £8 million, played 26 times for Harry Redknapp's team last term.