The Barcelona star failed to take the tournament by storm four years ago as the Maradona-coached Albiceleste reached the quarter-finals.
Cannavaro, who lifted the World Cup as Azzurri skipper in 2006, acknowledges that Messi is a brilliant player but considers the 1986 World Cup winner to have the edge - at least until the 26-year-old lifts the greatest trophy in international football.
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"But when you win a World Cup, a player becomes a legend. To be better than Maradona, Messi has to win the World Cup here in Brazil."
The former centre-back also mused over Brazilian talent, arguing that Neymar needs to show more graft in games and claiming that the defensive partnership of Thiago Silva and David Luiz has no equal in world football.
"Neymar still needs to work a bit harder," Cannavaro told reporters. "He's an excellent player, playing football that entertains people.
"The world is changing and football is too. The best defenders are currently from Brazil and the best strikers from Italy, Germany and other countries.
"Thiago Silva and David Luiz are very strong, they form a good team, perhaps one of the best in the world."