The Partenopei beat the Bianconeri in the Coppa Italiana final in May, and the two are joint top of the league after two games, and Mazzarri believes that the San Paolo outfit should always be in contention for honours.
"Napoli are a direct competitor to the top clubs and have been for years," he told Gazzetta dello Sport. "In fact, experts and commentators point to Napoli as the main rival to Juventus for first place."
And when asked whether there are other teams involved in the title race, he was emphatic: "Absolutely. There are teams equipped to do well until the end.
"I am referring mainly to Roma, but I think that Lazio have a strong team and should not be underestimated because they have found some consistency with their technical play, and [Miroslav] Klose has found form."Mazzarri will take charge of his 300th Serie A game as coach when Napoli travel to Parma on September 16.