Cassano expressed his disappointment with the appointment of new coach Max Allegri, who took over after Sergio Conceicao's departure on Friday.
Cassano and Allegri worked together when Milan won the championship over 14 years ago, and Cassano jokingly said that Allegri's success was due to his presence.
Leao saw the clip of Cassano's comments on social media and reacted with laughter, indicating that he didn't take Cassano's claim seriously.