Viktor Postol has taunted Terence Crawford ahead of their unification bout and claims the American is not even his toughest test.
WBC world super-lightweight champion Postol (28-0-KO12) takes on WBO holder Crawford (28-0-KO20) in Las Vegas on July 23 and will the hear the opening bell as a clear underdog.
Postol said: "What differentiates Crawford from many other fighters are his skills and technical attributes. From a mental aspect, he is a very clever boxer, always using his mind in the ring, changing stances, all the time adapting to different types of opponents.
"He has shown this in his previous fights. But that does not mean he is the best I have fought. I think Lucas Matthysse is a higher-level fighter than Crawford and everyone knows how my fight with Matthysse ended - with him knocked out and the WBC belt around my waist.
"That is exactly where the WBC belt will remain after my fight with Crawford on July 23. Just above the WBO belt. I am looking forward to destroying Crawford -- destroying his perfect record and destroying his reign as world champion."
The Ukrainian's coach, the legendary Freddie Roach, is equally confident of springing a surprise. He added: "Viktor will break him down just as he did with Matthysse. He has a lot of patience which comes from experience.
"He's going to break Crawford down brick by brick, with his jabs and his body shots. Viktor leaves nothing to chance. No one works harder in the gym than Viktor.
"I give Crawford a lot of credit for taking this fight but bravery will only take you so far in this game and in this fight it won't be taking Crawford into the winner's circle."
Postol will be making the first defence of his crown while 'Bud', who won a world title as a lightweight before stepping up, has stopped Dierry Jean and Henry Lundy since beating Thomas Dulorme to the vacant WBO title in April 2015.