The Gunners need to avoid a heavy defeat in Italy if they are to reach the last 16 of the competition.
However, Koscielny insists that the visitors will do their best to get the three points that would guarantee them a first-placed finish in Group F.
"After [losing] to Dortmund at home, it was important to play to win in Dortmund," he told the club's official website. "It was very difficult to win in Germany, because last season they were in the final of the Champions League.
"Napoli are a good team and very hard. We want to finish in first place in the group, so we need to win here."