"Napoli are a good team and did very well in the Italian championship."
Big-spending City go into the game full of confidence after making a perfect start to their league campaign with four wins out of four and Mancini believes the match practice will be an advantage against a team only one game into their season.
"Probably [it will help] because we have played five games (including the Community Shield)," the Italian said. "Napoli have played only one game, Wednesday is exciting for us but also for them."
Meanwhile, midfielders Gareth Barry and James Milner are both doubtful for Wednesday's game.
Barry has been out since sustaining an ankle injury on international duty last week while Milner suffered concussion after a clash of heads in
Saturday's win over Wigan.
Nigel de Jong (foot) remains on the sidelines while Italian striker Mario Balotelli is suspended after being sent off against Dynamo Kiev in last season's Europa League.
Like Mancini, defender Gael Clichy is aware of the tough challenge awaiting City ahead of their trip to Italy, and has rubbished the idea that Napoli are the weakest team in Group B with German side Bayern Munich and Spanish outfit Villarreal the other two sides.
"Napoli will be tough. If people say they are the weakest side in the group then that is the view of people who don't really know about football," said Clichy.
"They are a strong side and if you are at this stage of the competition and in the group, it means you have qualities.
"Champions League is a totally different kind of football. With hard challenges here, we have referees who will play on, but it is not like this in Europe. We have to be focussed defensively, and offensively we know we have players who can make the difference.
He added: "I am lucky enough to have been able to play in a few Champions League games for Arsenal, which was good, but I am aware it's a new competition for this club.
"It's not only me who has played in it before - Yaya (Toure) has won it. For us it may be one more game, like many we have played in the past, but we have to be aware it's a big part of City's season this year."
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