Milan announced Lucas Biglia will be out of action for approximately four months after surgery on a calf muscle tear.
The midfielder has been out since suffering the injury in training a week ago.
Tests confirmed there is a lesion to the area linking the tendon to the right calf muscle.
He went under the knife in Finland, as Professor Sakari Orava was chosen to perform the delicate surgery.
The prognosis is four months.
See the latest Serie A predictions and betting tips with Eurotips.co.uk