Milan confirm Rafael Leao picked up a thigh injury on international duty and will be out for at least a couple of weeks.
The striker was playing for the Portugal Under-21 team against the Netherlands yesterday when he sustained the injury.
A statement from the club confirms it is a lesion to the femoral bicep muscle in his right thigh.
Further tests will be performed in 10 days, meaning Leao is out of action for at least two weeks.
The 21-year-old has scored three goals and provided three assists in 10 competitive games for Milan so far this season.