Elie Baup's men have yet to record a point in Group E and are bottom following consecutive defeats to Arsenal and Borussia Dortmund, respectively.
However, while Benitez says he is taking nothing for granted, the Partenopei coach is nonetheless adamant his charges can triumph at the Velodrome.
"We have a strong team with a lot of character. I am convinced that tomorrow [Tuesday] we will show that on the pitch," the Spaniard told reporters. "It will be important for both teams to win, and we will make sure the result goes our way.
"Marseille have lost three games in a row so it will be even more difficult for us. They will want to show they can win the game, but we will show our determination. We are in the group of death as we call it."
Napoli skipper Gokhan Inler is anticipating a tough encounter in Marseille, but does not believe it is a must-win game for the Italians, even though they currently occupy third place and at present are not in position to progress to the last 16.
"We came here for a result. We are still alive in the competition and we will come to show our force," the Champions League winner said. "Tomorrow's game is very important but not decisive for us, we will have to show focus and determination.
"We will have to be focused from the start. It is a very important game for Marseille so we will have to be careful. We know the quality of their team. Like Napoli, Marseille have a very passionate crowd and stadium, we will be happy to play here."