Cassano joined Milan in January from Sampdoria and played a crucial role in their march to the Serie A title, scoring four goals and providing seven assists in 17 league appearances.
Allegri is impressed with the 28-year-old’s display for the former European champions but believes that given their firepower upfront that includes Alexandre Pato, Robinho, Zlatan Ibrahimovic and Filippo Inzaghi, he will have to compete hard to play week in week out next season.
"He [Cassano] scored four goals and made eight assists and that was after two months of inactivity so I'm happy with him," said the Italian tactician, according to AFP.
“Without taking anything away from Sampdoria, where Antonio was the star alongside [Giampaolo] Pazzini, here at Milan we have many stars and there's a lot of competition so there's a chance he won't play."
Allegri has also warned Brazil international striker Pato to amass more consistency in his game despite scoring 14 goals and providing four assists in 25 Serie A matches this campaign.
"He's done a lot but the way he played in the derby and against Fiorentina, he must do so 30 times [a season]," said the Milan coach. "He doesn't need to manage himself because he's only 20 [actually 21].
“He needs to add useful movement to his great attributes without getting confused. He has incredible quality and could become much more than he is already."