The Holland defender missed the game, with Juve insisting he had been struck down by illness.
However, Tuttosport says Sarri and De Ligt agreed for him to sit out the game due to some niggling injuries centred around his shoulder and thigh. Sarri feels the problems have influenced the defender's scratchy form.
His opinion was accepted by De Ligt, who also believes he needs to get himself in better shape to do himself justice.
The young centre-half isn't expected to be seen again on the pitch for at least fortnight.