An impressive 2-0 victory at eventual champions Bayern Munich in March proved the catalyst to the superb winning streak, which this term has seen Fenerbahce, Fulham and Sunderland fall by the way side.
Arsene Wenger's side are hoping to add Marseille to their impressive list of conquests this evening as their Group F campaign kicks off at the Stade Velodrome.
It is a match of significant importance as sterner tests against Borussia Dortmund and Napoli await, with centre-back Mertesacker confident of collecting another important win.
"We have an exceptional team - that's the main thing," the Germany international said.
"We built up confidence from last season, especially the last 10 games when we didn't lose anything.
"You could feel it from the first day that there is something special in this team, apart from the first game [against Aston Villa], no one dropped and the performance went well after that.
"We have shown so far that we are ready to keep our confidence and keep the run going. The most important thing is to keep that mental level high and to be prepared for because it will be hard.
"They will put pressure on us so we need to be aware of that, particularly in the first 15-20 minutes."
Ozil, signed to much fanfare on transfer deadline day, travelled to Marseille after struggling with tight muscles following his superb debut in Saturday's 3-1 win at Sunderland.
Giroud, who suffered a knee injury at the Stadium of Light, has also been passed fit, but Arsenal's squad still looks threadbare.
"The situation of the other players is we had some small knocks but they look okay," boss Wenger said.
"But of course I am concerned because from now they play for two months every three or four days and it's important we get some players back because you cannot play for the next two months with the squad we have at the moment."
In the meantime, though, Wenger hopes his depleted squad can secure an opening-night win in what is sure to be an intimidating - if half finished - Stade Velodrome.
"There is a passionate home crowd here in this city and then the team of Marseille have a compact game," he said.
"They are very good defensively, they are very strong physically and have this experience of playing big games in their stadium.
"And then you cannot forget about their offensive players like Mathieu Valbuena, Andre-Pierre Gignac etc."
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