Giovanni Galli says Max Allegri is successfully transforming AC Milan after their victory over Napoli.
Milan were good value for Sunday's 2-1 win at San Siro stadium.
Afterwards Galli, who was goalkeeper for both Milan and Napoli, told Rai Radio 1: "Allegri's influence is evident. The team has acquired a keen understanding of the game and has brought in top-level players like (Luka) Modric: yesterday, in terms of dynamism, it seemed like he had only played a dozen games in his career and not a thousand.
"A solid Milan, without frills, the team is proving to be solid and aware of its strengths and weaknesses. Milan could be the big surprise of the season."
Asked if Napoli have gone backwards, Galli insisted: "No, Napoli is also a strong team. Yesterday they conceded the goal just as they were taking control of the game. They have mastery and awareness of their resources.
"In the second half they had clear chances to equalise. In short, Napoli are on track despite this defeat. Milan and Napoli have something more than Inter, Roma, and the others."