The Gunners are currently top of Group F with seven points and a win against Marseille, who are second with six points, will virtually guarantee qualification for the London side with two games remaining.
Wenger is prepared for a demanding game of concentration on Tuesday night against Marseille, whom he believes will be a threat on the counter attack.
"I believe they have a team who are certainly more at ease at home than away from home," he said in a press conference, "because they are a side who can defend well, who is very physical and is quick on the break so I believe counter attack suits them more than dominating the game."
Marseille and Arsenal both have had a difficult start to the season but like Arsenal, the French club has gained momentum ahead of the clash in London with two domestic wins and that has not gone unnnoticed to Wenger.
He continued: "They've gained in confidence as well between the two games, like we did, so it should be an interesting tie. But for us it's an opportunity to qualify tomorrow night and of course we want to take this chance."
Wenger will be hoping to guarantee qualification before Arsenal play Dortmund at home and travel to Olympiacos in their last two fixtures.