However, Mancini, who coached Inter Milan in his homeland from 2004 to 2008, thinks that Rafael Benitez's side will break Juve's winning streak next term.
He told Sky Sport 24: "For Allegri, it will be difficult, but he will be proud that he gets the opportunity to coach such a club.
"He will not need a huge amount of squad strengthening to compete for the title, although this year I have different winners in mind: Napoli.
"They excite me more. Benitez knows the team and they intend to strengthen. They will fight with Juventus, Roma and perhaps AC Milan."
Juventus have won the last three Scudettos.