The Italy international regrets not having put in more effort during his younger days, while also admitting that he has grown weary of "fake people" in football
The forward seemed destined for greatness when he exploded onto the Serie A scene with his native Bari some 14 years ago but, despite subsequent spells at Roma and Real Madrid, he never realised his full potential, with many putting that down to a bad attitude, particularly towards training.
Cassano got his act together in recent years, winning a Scudetto with Milan and helping Italy reach the final of Euro 2012, but he freely admits that he wasted his best years.
"It's my fault if I haven't have a better career," the Inter attacker told Confessione Reporter. "I have done 50% of what I could have done. I always had a unprofessional way of training.
"I thought that one could go forward with quality alone. I played in great teams but always did so little.
"99% of the time it was me who messed up. However, there were others put me in a position to mess up."
Indeed, Cassano says that the modern game is full of people who are only out to help themselves.
"I tell my children that the most important thing is not playing football," he revealed. "I have grown tired of this game. There are too many fake people."
The 30-year-old, who was twice named Serie A young player of the season, has been capped just 35 times by his country.