De Napoli began his football career with Rimini Calcio in Serie C, under manager Arrigo Sacchi.

De Napoli often played alongside Salvatore Bagni in midfield, serving as a defensive foil to the club's star playmaker Diego Maradona.

During his six-year spell in Naples, De Napoli won the scudetto in 1987 and 1990, the Coppa Italia in 1987, the UEFA Cup in 1989, and the Supercoppa Italiana in 1990.

He was adept at winning back possession to support his more creative team-mates while also functioning as a deep-lying playmaker thanks to his range of passing and accurate long balls.

He also possessed a powerful and accurate long-range shot and was known for his ability to make attacking runs and charge forward with the ball from deeper areas of the pitch.