The Portugal forward headed through the limp hands of Milan goalkeeper Gianluigi Donnarumma just after the hour, which was enough to settle a low-key affair.
Juve could have won by a more comfortable scoreline with Douglas Costa and Joao Cancelo having decent chances, while the Bianconeri twice correctly had goals ruled out for offside before Franck Kessie was deservedly sent off for Gennaro Gattuso's side.
