Balotelli had a spell with Barca as a teenager before committing himself to Inter Milan.
Barca youth coach Fran Sanchez told Sport: "It was not too many days, three or four workouts and a tournament.
"He seemed a quiet boy, spoke little, also the language barrier, but he was very well behaved at all times. His attitude was good."
He added: "There was no agreement on economic conditions between the club and their representatives. It was not a sport decision."