Walter Mazzarri feels Napoli may be in better shape than Chelsea but is wary of the threat posed by Andre Villas-Boas' men ahead of their UEFA Champions League showdown.
The Blues travel to Italy on Tuesday for the first leg of a last-16 tie between two sides that have fallen off the title pace in their respective domestic competitions.
But while Napoli have started to regain form in recent weeks, Chelsea have continued to struggle for consistency and the future of manager Villas-Boas has become an increasingly hot topic.
Mazzarri, who will be banned from both matches against Chelsea, is happy with how his team have prepared for the clash.
However, he expects a tough encounter and has rejected suggestions that Napoli will be facing a side in the middle of a crisis.
"We went through a negative period, but that is something that every team has at times," Mazzarri told Rai Sport.
"We kept conceding at the first opportunity, but now things are changing. Things go better for us, partly because we work on them during the week.
"Perhaps we are in better shape than Chelsea going into this game, but they have champions who are accustomed to playing a certain level of game.
"On Tuesday they know that they cannot make a mistake, so will become unified and I doubt we'll be facing a team in crisis. Naturally, at this level you need a bit of luck too."
Napoli progressed to the knockout phase from a tricky group that also contained Premier League leaders Manchester City, but Mazzarri knows it will require a considerable effort to go any further in the competition.
"I do not agree that Napoli are favourites," he added on Sky Sport Italia.
"It will be a terrible test, in order to pass it we must do something extraordinary."