The Brazilian is fuming over claims made by Matheson that he had agreed to sign with the ambitious new A-League franchise before he penned a new deal with Adelaide.
"All of this is not true," Cassio told the Sunday Mail. "I'm very disappointed. "I never spoke with this man (Matheson). I've only talked to one agent (working for North Queensland).
"I never said I will go or I will sign.
"For me words are like a signature. I never said I will go because I respect Adelaide."