Balotelli's future at City is up for debate after his latest red card this week.
"He can become as good as he wants," Zola told the Daily Mail. "Everything is in place except the self-discipline. He is a skilful player, a strong player; he just needs to learn the self-discipline that is so important in achieving results.
"All the biggest players I've seen in my career had talent, but they also had strong self-control which made them key players. I think Mario knows that, and he has to learn to use his passion for football in the best way."