City can clinch a place in the knockout stage of Europe's elite competition with victory over their Group A rivals at the San Paolo Stadium.
Yet anything less would give Napoli a chance and leave City with the daunting task of having to beat Bayern Munich in their final game to guarantee progress.
The atmosphere in Naples is likely to be intimidating and the reputation of an extreme element of the home support has also led to City issuing safety advice to travelling fans.
De Jong said: "There is going to be an intensity because they are fighting for the last chance.
"Everybody knows the stories about Napoli and their fans. It is going to be an exciting game.
"Hopefully everybody can remain quiet and go there for the football game.
"We have to be focused on that. As long as the challenge is on the pitch I will be up for the task.
"Let's just do the talking on the pitch. That goes for the whole team."
Despite their domestic dominance - City now lead the Premier League by five points after 12 games - Roberto Mancini's men made a stuttering start in Europe.
They were held by Napoli in their opening game at the Etihad Stadium and a defeat in Munich left them with much to do.
Back-to-back wins over Villarreal have got the campaign back on track, lifting City to second in the group, but the Napoli trip has long looked like being the key fixture.
Holland international De Jong, 26, said: "It was always going to be a hard game, especially away and that atmosphere.
"We have to be focused and not concede. As soon as you concede it will be hard to score, but we are confident.
"I am confident to be able to play my part. It is up to the manager."
City have broken into a considerable stride since their loss in Munich, winning their last nine games across all competitions.
Goals have flowed, with the team scoring at least three in all but one of those games, the highlight being a remarkable 6-1 derby win over Manchester United.
De Jong said: "We already had the belief before the 6-1 but after that game, the confidence did get higher.
"Away games are always more difficult, especially there [Naples].
"But this is not going to be an easy task with their fans. We just have to be confident.
"It will be a different game to the game at home. We just have to be 100% focused, otherwise you will concede goals you don't want to."