The veteran striker, 34, signed for Genoa yesterday to the end of this season.
Former defender Gastaldello played with Balotelli at Brescia and told TMW: "As a player, Mario has always been a great talent, I think this is a great challenge for him. Everything will depend on his will and his desire to challenge himself in a team that needs to save itself.
"He certainly won't be able to be at the same level as the others. The game is always the game, you have to play to get into top form. He'll need a bit of time, also given his physique, but he has quality and can be decisive even during a game with just a few minutes.
"Over time, wrong things have also been said. He certainly made mistakes in many things, but I like to judge a person when you know them and when you live with them. Mario has never had wrong behaviors with us, we had a good relationship, both me and the rest of the team. Then, regarding private life, everyone is free to decide and do what they want."