Arsène Wenger says Arsenal face one of the defining matches of their season against Napoli and that qualification to the Champions League last 16 would give them a lift before the Premier League fixtures against Manchester City and Chelsea.

The manager has brought his strongest available squad to southern Italy and he indicated that he was loth to make too many changes to the team that drew 1-1 at home to Everton on Sunday. Arsenal must avoid a three-goal defeat to ensure they advance but a draw would guarantee that they did so as group winners.

Arsenal would almost certainly face more fearsome last-16 opponents as runners-up but Wenger's message was clear: focus on the details, play the football that has made them England's best team and keep a key element of the season alive into the new year.

"Will the next three games define our season? Tomorrow's game certainly [will]," he said. "It is to be in the Champions League or not. The other two games will not definitely … we are five points ahead and the championship is a marathon. We will be in the race, no matter what happens but they [City and Chelsea] will hopefully show our strength. Napoli is a decider, that is for sure.

"Our priorities are simple: first, qualify and, if possible, top. If we finish top, it's even better. We can't afford to do anything [regarding rotation]. I rotate a little bit sometimes [but] never more than two or three because stability is important. We'll have to keep [Gonzalo] Higuaín quiet he is very dangerous and the more we can play outside of our box, the easier that will be. We have to be at our best. An average performance will not be good enough."

Arsenal have made special security provision for their 700 travelling fans, in light of the violence between supporters that marred Napoli's last home Champions League tie, against Marseille. The club will provide coaches to transport the fans to and from the stadium.