Arsenal and Marseille will both look to put aside domestic struggles and take control of Group F when the pair meet in a Champions League match on Wednesday.
Marseille leads with six points, Arsenal has four points, Borussia Dortmund is third with one point and winless Olympiakos is last.
Arsenal has never lost in seven trips to France and is keen to avoid a similar drop-off to last season when it won its first three matches before fading to finish second in its group. That condemned it to a knockout stage matchup with eventual champion Barcelona.
"It must be our aim to win the group, especially after what happened to us last year when we were not top of the group," Tomas Rosicky said. "In the last three games we messed up."
Marseille has won both of its Group F matches without conceding a goal, but remains on guard against an Arsenal side that is beginning to find its way with four wins in its last five overall.
"Marseille are a direct contender for us," Rosicky said. "It's a big game and we want to be successful there."
While Arsenal is finally recovering from its poor start domestically after Sunday's 2-1 win against Sunderland put it mid-table, Marseille hasn't as it sits just one point above the relegation zone in Ligue 1.
"We're still far from being qualified yet because on paper Arsenal is the strongest team in this group," Marseille coach Didier Deschamps said. "In general, you need 10 points to qualify. We have a cushion but we'll have to go and get more points."
Marseille has won only one of 10 matches in the French league and drew 0-0 with Toulouse on Saturday to trail leader Paris Saint-Germain by 14 points.
Still, Arsenal manager Arsene Wenger remained wary ahead of the trip to the Stade Velodrome despite the French club's poor domestic form.
"Marseille can be dangerous because they are good on the counterattack," Wenger said. "I think at home they will try to play like that against us.
"The two games against Marseille will decide our qualification. If we take four points, then we will qualify."
Arsenal remains without midfielder Jack Wilshere (ankle) and defenders Thomas Vermaelen (ankle) and Bacary Sagna (fibula), while leftback Kieran Gibbs and midfielder Aaron Ramsey are doubtful to return.
Marseille forward Jordan Ayew and defender Rod Fanni are suspended for that game.
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AP Sports Writer Steve Douglas contributed to this report from London.
