Zimbabwe-born boxer Dereck Chisora who is now fighting as a Briton on Tuesday dismissed Wladimir Klitschko as someone who has mainly fought “taxi drivers” before their world heavyweight title fight on Saturday.
Chisora, 26, will challenge Klitschko, 34, for the Ukrainian’s IBF and WBO heavyweight belts in Mannheim, Germany.
“It’s time for you to have a proper fight,” Chisora told BBC Sport.
“You are on the way down and I am on the way up. You’ve never boxed anyone like me.
“I am young, I move my feet, I am fast. I am a different heavyweight.
“I am here to take the title back to Britain.”
Klitschko instead praised Chisora, claimed he was better than David Haye, but also described him as horrible.
“He is a very special man with pretty good skills, he is much underestimated,” said Klitschko.
“As a boxer he’s got pretty good skills, determination. He’s a very busy fighter, so there will be a lot of action on Saturday.
“He’s better than David Haye, he is as good at promoting himself but he even shows up for the fight.
“As a fighter I think he’s talented. I think he’s better than David Haye.
“Chisora the person is full of garbage, so I have got to care about the boxing stuff. He’s going to give me a good challenge in the ring.
“I think he’s going to start pretty good, but he’s going to end up pretty bad.
“He says I am an old man going down and he’s a young man coming up.
“That’s a lot of talk, but I will also ask him please don’t miss the last press conference before the fight because there are a couple of things I really need to tell Dereck Chisora.”
Klitschko was set to fight WBA champion Haye last year before the Englishman pulled out with a back injury and negotiations have repeatedly stalled since then.
Chisora is giving up 13,97cm to the 198cm Klitschko and has had 14 fights (all wins) to Klitschko’s 58 (55 wins, three defeats).
However, Chisora’s trainer Don Charles rejected suggestions his fighter’s chance had come too soon.
“How do you get experience?” said Charles. “By doing the task. He has got the style to do it.”
But Klitschko’s trainer Emanuel Steward said his man had been upset by Chisora’s “disrespectful” pre-fight rhetoric and warned the challenger to expect “a much more aggressive Wladimir”.
Chisora’s last fight was a ninth-round stoppage of Norwich’s Sam Sexton on September 18, while Klitschko knocked out Nigeria’s Sam Peter in the 10th round a week earlier. Chisora is 6-1 to win Saturday’s fight.