With a four-point lead over Milan ahead of their trip to the San Siro, Mazzarri has declared that his side are aware of that game's importance in the chase for Champions League places.
He told Sky Italia: "We are going through a good period of form and I was happy that we kept a clean sheet. Genoa are a quality side and we did well to dominate them.
"We will prepare with real focus, as the Rossoneri have fought back remarkably well to catch up numerous sides. I don't have to do much work firing them up for this game, as they know full well what it means.
"We already have more points than at this stage last season and are growing constantly, so it is fundamental to achieve Champions League qualification. Napoli have returned to being aggressive and determined, but above all sharp physically."
Mazzarri's men sit second in Serie A with 62 points from 31 games.