The Italy international has warned that Walter Mazzarri's men will not be pushovers, and has been impressed with the Partenopei's rise in recent years.
Just six points separate the two sides going into the San Paolo fixture, and the Italy international has been impressed with the Partenopei's rise in recent years.
"The match could go either way. It won’t be decisive because there is still a long way to go in the championship, but it will of course be important for both teams," Chiellini told Sky Sport Italia.
"Napoli have improved immensely. They have an ambitious president, and since [Walter] Mazzarri arrived, they’ve taken a further step up in quality. The club has not only become competitive in Italy, but also in Europe, as they showed last year over two legs against Chelsea."