Marseille, the 1993 champions, have won only one Ligue 1 game this season although they lead Champions League Group F with six points from two games, having crushed Borussia Dortmund 3-0 in their previous match.
Arsenal, who have yet to win the Champions League, are second on four points in the group and lie 10th in the Premier League standings having had trouble adjusting after Samir Nasri and Cesc Fabregas left during the off-season.
Victory would give Marseille a perfect record midway through the group phase. Didier Deschamps's side, however, will need to improve dramatically from their dull Ligue 1 displays if they are to challenge the Londoners.
Marseille, 15th in the French league, drew 0-0 at Toulouse at the weekend and have not won a league match in almost a month.
"I don't want to be too pessimistic [about our situation]," Deschamps told the club's website. "I'm aware of the difficulties we are facing but we are working on that and we are trying to build some confidence."
Arsenal can empathise with their rivals' predicament.
"Marseille is a good team but they are under pressure a little bit like we are in the league because they didn't start as strong as they would have expected," said Arsenal coach Arsene Wenger.
"That puts more pressure on you. They have done well in the Champions League, certainly, because it is a competition where there is a bit less expectation and they are less under pressure."
RENEWED OPTIMISM
Although Arsenal won 2-1 against Sunderland on Sunday their performance was far from convincing and owed a great deal to an outstanding performance from Dutchman Robin van Persie who scored twice - the first time after only 29 seconds, the second from a brilliant free-kick - to give Arsenal only their third league win of the season.
The three points moved them up five places in the table, which gave Wenger renewed cause for optimism.
"We have now won five games on the run at home," the Frenchman said.
"I think the attitude and spirit of the team is great. The motivation is there, the quality is there, so slowly we are getting better."
The Gunners' injury problems have deepened, however, with defender Kieran Gibbs and midfielder Aaron Ramsey joining the already lengthy list of absentees.
Ramsey missed Sunday's game with a hamstring injury while Gibbs was replaced by Andre Santos five minutes into the second half after suffering a stomach injury.
Arsenal are already without defenders Thomas Vermaelen and Bacary Sagna while Laurent Koscielny and Johan Djourou have only just returned from injury.
Wenger, back in the dugout after his two-match Champions League suspension against Borussia Dortmund and Olympiakos, told reporters: "Gibbs has an inflammation of his stomach muscles and only has a small chance of playing on Wednesday.
"Ramsey has a small chance of being in the squad. He had fatigue of his hamstring. I wanted to giv
