Marek Hamsik and Paolo Cannavaro scored the goals that saw the Partenopei overcome Catania at the Stadio San Paolo.
Mazzarri warned his side that every game from now on will be fiercely contested as they compete for the Scudetto.
"I cannot change my attitude by looking at the table," Football Italia quotes Mazzarri as saying.
"Our results come from battles like the one we had today and we must not get distracted. We need to remember every game is a battle."
Juventus face Chievo in Verona this afternoon.