Reports in Italy had indicated that the Spaniard, who is on loan from Chelsea, would be given a final chance by coach Filippo Inzaghi after scoring just once since his arrival at the club.
Last week's triumph made it four games unbeaten for Milan, who currently sit in fourth place in the Serie A table.
Fiorentina have taken their time to find their feet this campaign, but three victories in four games in all competitions suggests that they could be ready to make their move up the standings.
Viola, who are in 11th position, thrashed AC's rivals Inter before the international break, meaning that they will be targeting a Milan double on Sunday.
AC Milan: LDDWW
Possible starting lineups
AC Milan: Abbiati; Alex, Rami, Abate, De Sciglio; Essien, Muntari, Poli; Honda, Fernando Torres, El Shaarawy
Fiorentina: Neto; Rodriguez, Tomovic, Savic, Marcos Alonso; Pizarro, Aquilani, Fernandez, Cuadrado, Valero; Babacar
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