BRITAIN’s Dereck Chisora has reiterated that he plans to knock Vitali Klitschko out in the eighth round and claim the Ukrainian’s WBC heavyweight crown. The Zimbabwe-born fighter takes on his 40-year-old Ukrainian opponent in Frankfurt on Saturday. Chisora, 28, is widely regarded as the underdog in the WBC heavyweight championship fight, but he is promising to silence his doubters. "I will end the Klitschko reign and cause a massive upset,” he pledged.  Klitschko is yet to be knocked down in any professional fight, or lose on points but Chisora, who stands six inches shorter than his opponent at 6ft, professes to be undaunted. "Vitali has been around a long time. He’s the king of the sport but it is time someone came in who is young and fresh,” said Chisora. "It is the end for Vitali, I promise you. I will end the Klitschko reign and cause a massive upset in my magic eighth round. It will be felt around the world. Chisora is looking to bounce back from a controversial points defeat by Robert Helenius in December - he also lost to Tyson Fury in their British title showdown in July last year. Three-time world champion Vitali knocked out Britain’s Herbie Hide in London in June 1999 to claim the WBO title and also saw off a challenge by Danny Williams in 2004 but was beaten by Lennox Lewis when they clashed for the WBC title in 2003.