Rafael Benitez's side have won two of their three UEFA Champions League Group F encounters but sit third, behind leaders Arsenal and Borussia Dortmund on goal difference.
In a match that could prove crucial in their hopes of reaching the round of 16, Napoli are heavy favourites to beat struggling Marseille.
The French side have lost all three of their Champions League fixtures and have slid to fifth in Ligue 1 after a dreadful run of form that has seen them fail to win any of their last six matches in all competitions.
However, Benitez - who won the Champions League with Liverpool in 2005 - believes Marseille's plight will make the fixture even tougher for his side.
"We have a strong team with a lot of character," Benitez said.
"I am convinced that tomorrow (Wednesday) we will show that on the pitch. 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 (in the Champions League) 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 have not lost any of their five previous home games in the Champions League, winning four, and defeated Marseille 2-1 in France last month thanks to goals from Jose Callejon and Daniel Zapata.
Callejon has now scored eight goals in 12 appearances in Europe's premier club competition, with seven of them coming for former club Real Madrid.
Napoli have not lost a Serie A match at home in 2013, winning 14 of 16 encounters, and they defeated Bologna 2-0 on Saturday.
Miguel Angel Britos (collarbone) and Camilo Zuniga (knee) are on the sidelines for Benitez's men, though.
Marseille ended a five-match losing streak at Rennes on Saturday but needed goalkeeper Steve Mandanda to save a late penalty to earn a 1-1 draw.
Jordan Ayew scored his first league goal since January in that clash, but the pressure on manager Elie Baup has not eased, with Marseille having won just twice since the start of September.
They have kept just two clean sheets in the last two months and will need a miracle if they are to become just the second team ever to qualify from the group stages after losing their first three matches.
The feat was achieved by Newcastle United in the 2002-03 season but, in a group that also contains Arsenal and Borussia Dortmund, a repeat is unlikely.
Marseille will be without Lucas Mendes (ankle), while defender Rod Fanni (adductor) is unlikely to feature.
