The British fighter made the claim ahead of the bout in Munich on February 18.
Chisora said: "Vitali is going down in the eighth round.
"Number eight is my lucky number. He just does not know what is coming - I am coming to take what is his and make it mine."
Klitschko recently responded to claims that his age may be a factor ahead of the fight.
Chisora will be looking to return to winning ways following a controversial points defeat against Robert Helenius in December.