The Uruguayan striker's future has been the subject of speculation throughout the summer, with reports of interest from Real Madrid, Manchester City, Chelsea and Paris Saint-Germain.
Former World Player of the Year, Cannavaro, feels that replacing the potentially outgoing Cavani with City forward Dzeko would be the right choice.
"I think Dzeko could be the right choice, but it will be difficult [to replace Cavani]," Cannavaro told reporters in Naples.
"When a player like Cavani leaves, after they have already lost Ezequiel Lavezzi last year [to Paris Saint-Germain], it is clear there will be great disappointment.
"These are signals that suggest you do not think about the future. The fans rightly want to win the league and the cup and always hope to achieve the best. Replacing Cavani is not going to be easy."
Cannavaro played for Napoli from 1992 to 1995.