Mancini said the 20-year-old Italian, who has scored two league goals since joining City from Inter Milan in the close season, still has some way to go before he can compare himself to the mesmerising Barcelona forward.
"I like that a player is confident in himself... (but) only if you play well every game and you score every game maybe you can say this," Mancini told a news conference.
"If he thinks what he said I think he must show (it) every game."
"You need to smile to play football. That is the best thing you can do," he said.
Earlier this week when picking up an award for European under-21 player of the year, Balotelli was quoted by local media as saying: "There is only one player who is a little stronger than me - Messi. All the others are behind me."
Mancini's other striker to have made headlines this week is Carlos Tevez, who on Monday completed a U-turn as he committed to the club a week after handing in a written transfer request.
"I am happy we finished this situation and don't want to speak about this until the end of the season," he said.
