Former Chelsea boss Maurizio Sarri is being treated for pneumonia.
The 60-year-old Juventus coach spent Monday morning at the Italian club having missed a weekend friendly against Triestina because of what was initially thought to be flu.
After feeling unwell, further tests diagnosed pneumonia and Juve confirmed treatment had begun.
Juventus visit Parma for their opening Serie A match on Saturday and it is not clear if Sarri will be in charge.
He succeeded compatriot Massimiliano Allegri at Juventus in June.