The midfielder, who has been heavily linked with a move to the Premier League with Arsenal, played a starring role for Portugal during this summer’s Under 21 European Championship.
However, the 23-year-old appears to have picked up the problem during the tournament in the Czech Republic with the injury only becoming apparent on his return to pre-season training.
The midfielder will now miss pre-season and the start of the new campaign with Sporting expressing their disappointment at the news with a statement on Facebook.
“Sporting hereby express their indignation that William Carvalho has returned with a stress fracture of the tibia without this having been reported by the clinical staff of the National Under-21 team or any of its officers to the management of Sporting," the statement read.
“Only yesterday, Monday, on the return of William Carvalho to training the medical staff of Sporting identified an issue with the player and, curiously, only today at dawn the Portuguese Football Federation sent Sporting clinical newsletters referring to the seven Sporting players who participated in the Under-21 European Championship .
“The clinical report selection, referring to William Carvalho, says the player never had any physical problem . The player denies this and says that the clinical department was aware of the player's complaints.
“As a result, the player William Carvalho faces a spell out of between 10 to 12 weeks.”