Vitali Klitschko has questioned David Haye's credentials as a heavyweight ahead of Saturday's fight with his brother Wladimir.
Haye stepped up to the top division after winning three world titles as a cruiserweight and he quickly acquired the WBA title following a points win over giant Russian Nikolay Valuev.
But the Londoner will again give away a big weight advantage to his opponent when he battles Wladimir Klitschko in this weekend's Sky Box Office clash.
And Vitali feels Haye will never be a genuine heavyweight and is confident his younger sibling will make his superior size count in the ring.
"David Haye is too light, simply too light," the Ukrainian told Sky Sports News. "It's not a real heavyweight. He came from cruiserweight.
"You have to be an original heavyweight like Wladimir, who has fought in the same division all his career. David's too light."
But the older Klitschko admits Wladimir will have his hands full against Haye.
"It will not be an easy fight," he added. "It will be a very interesting fight. Nobody in the world, no expert can predict the heavyweight division where every punch can make a decision."
