Mazzarri believes that Napoli must maintain their focus in the final eight games and look to second place as a minimum expectation.
He told Sky Italia: "Atalanta barely went past the centre-circle, but unfortunately we pay for every mistake that we make at the moment. The lads were afraid and during the break I urged them to shake off the outside world and think only of the football.
"With the great strength of this group, we were able to bring home the victory. Goran Pandev needs a good pitch to give his best and he benefited from it today. I am happy he scored, as he had been very unlucky recently.
"We are not already thinking about the game with Milan. We had the same discussions before the Juventus match and then we dropped points against Udinese and Sampdoria, so we have to take it one game at a time."
Mazzarri's men are two points ahead of Milan in third and meet the Rossoneri next month.