Mancini, who saw his own team knocked out in the group stages of Europe's elite competition, believes that the Stamford Bridge club could be there for the taking ahead of Tuesday's last 16 clash at San Paolo.
The Blues have gone four games without a win, including Saturday's home draw with Birmingham in the FA Cup, and Mancini is adamant that Chelsea "have problems".
He told Il Mattino: "They have problems, have not won a game for some time and it is clear that they are in trouble. But I would not put too much trust [in their supposed crisis].
"It is true that Napoli are a side who are able to score anywhere, but to go to London with Chelsea obliged to overturn the result of the first leg would give [coach Walter] Mazzarri's team a great advantage.
"At Stamford Bridge, Napoli would be lethal on the counter-attack."