Cassano used his Inter presentation to take aim at Milan and directors.
Allegri hit back: "He was an important player in his first six months here and contributed to the Scudetto victory. He started really well last season and was stopped by this heart problem, but I think Milan really helped him be passed fit to continue his career.
"We helped him to reach the Euros, because without Milan he would never have played for the Nazionale in 2012. Then he put in a transfer request and the club accepted it.
"Cassano played pretty often with me, as did all the players, though I can't just let anyone take part in 60 games per season. The facts show when he was fit, I always let Cassano play. If he wanted to feel first choice in every match, then you'd have to ask him that.
"I guess Cassano is happy to join Inter and we are happy to have Giampaolo Pazzini. Divorces exist in life. Was he ungrateful? Antonio knows full well what Milan did for him and vice-versa. It's too easy to talk when you've left a club. You need to show a basic level of respect."