The 22-year-old Italian faces a late fitness test on his injured back and may be unfit for City's Champions League game against Real Madrid at the Etihad Stadium on Wednesday.
But while a doubt remains about his immediate fitness, his compatriot Mancini is in no doubt about his talent, although he does question his mental approach to the game.
Talking to reporters at the club's Carrington training ground outside Manchester, Mancini said: "He has everything to be one of the best players in the world.
"He could be like Cristiano Ronaldo or Lionel Messi if he understands that to be like this you should work hard."
Mancini and Balotelli have been likened to having a father-and-son relationship with Balotelli's unpredictable character causing problems on and off the field.
In April, when Balotelli was sent off in a defeat at Arsenal that looked like costing City their chance of winning the Premier League title, Mancini said he would definitely sell him.
But almost nine months later Balotelli is still there, if, at times, a peripheral figure in Mancini's plans.
Revealing the frustrations of working with him, Mancini said: "It is not easy to work with him every day because if you are a manager, you should manage 22 players.
"Mario outside the pitch is a fantastic guy. Sometimes he doesn't understand how his job is important for his life but I hope he can understand this quickly.
"He is 22 but life can go quickly. He needs to understand that to be like Ronaldo and Messi he should work hard, his mind should be always on his job, not on the other things that are not important."
City must beat Real to have any chance of overturning their poor start to their second Champions League campaign and advance from Group D.
They have drawn their two home matches against Borussia Dortmund and Ajax Amsterdam, and lost their away games at Real Madrid and Ajax and are bottom with two points. Borussia top the table with eight, followed by Real on seven and Ajax on four.
But if City win their last two matches and other results go their way they could still qualify for the last 16, although, as Mancini also said on Tuesday, "It is very difficult, but we will do what we can."
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