Real Madrid faces its most important game of the season on Tuesday night when it travels to play Olympique Marseilles in the last game of their Champions League qualifying group.

Madrid needs to win in Marseilles to assure finishing top of the group. That would mean a theoretically easier group in the knockout stages of the competition, as well as the advantage of playing the return leg of the next round in the Santiago Bernabeu Stadium.

However, the Spaniards also know that they have to avoid defeat by three goals or more. That result, coupled with a win for AC Milan against a weak Zurich team would see them knocked out at this early stage of the tournament.

With this season's final being held in the Bernabeu that would be a huge humiliation for the Spanish giant, that has spent over 250 million euros this season.

In France, Real will have to contend with a hostile atmosphere in the 50,000 capacity Stade Velodrome, while former Real Madrid striker Fernando Morientes is a member of the French side.

Madrid coach Manuel Pellegrini has injury problems for the trip. Kaka is not traveling because of a pelvic injury, while central defender Christoph Metzelder is also out, as are Guti and Ruud van Nistelrooy.

Cristiano Ronaldo will travel and will no doubt be looking to make up for the petulant display that saw him sent off in last Saturday's BBVA Primera Liga win against Almeria.

Elsewhere Atletico Madrid has to beat Porto to assure third place in its qualifying group. By finishing third Atletico assures the consolation of a place in the next round of the Europa League.