Maurizio Sarri has been diagnosed with pneumonia and may not be able to take to the dugout as Juventus travel to Parma on the opening day of the Serie A season.
It was initially believed that the 60-year-old was suffering from flu, but further tests have revealed the extent of his illness.
The Italian has been unable to take training and could miss another week as he follows a seven-day course of antibiotics.
Sarri returned to Serie A this summer after just one year in England with Chelsea, for whom he secured a third-placed finish and won the Europa League - his first trophy as a manager.
The former Napoli boss will be hoping to win his first Serie A title this season, having finished second to Juventus in his time at the San Paolo.
