Cristian Zapata suffered a thigh injury in AC Milan's Serie A win at Genoa, the Rossoneri announced on Tuesday.
Zapata was hurt in the opening stages of Monday's game and had to be replaced by Andrea Conti in the 14th minute.
Milan released a statement that said a scan diagnosed Zapata with "a lesion of the biceps femoris muscle of the right thigh".
He will be assessed again in a fortnight, meaning Zapata will be out for at least Milan's next two matches, which are both against Napoli.
Gennaro Gattuso's side face Napoli at home in the league on Saturday before meeting them again three days later in the Coppa Italia at San Siro.
Zapata, who has been linked with a January move to Fenerbahce, has made 10 Serie A starts so far this season, with Milan fourth in the table after beating Genoa.