Wladimir Klitschko (59-3, 50 KO) has been the dominant force in heavyweight boxing for the past several years. He hasn't lost a fight in nearly eight years and has dominated every opponent put in front of him during that time period.
As the IBF/WBA/WBO world champion, his reign is virtually undisputed. The only man who can make any sort of legitimate claim would be older brother Vitali, and challengers have been in short supply of late.
That has forced the champion to line up and knock down a series of retreads, unknowns and no-hopers who have all but killed interest in heavyweight boxing.
But that could be about to change. There are finally on the horizon several young heavyweights who, if managed correctly, could well find themselves, if nothing else, live dogs against the champion.
These five men are the biggest challenges to Wlad's heavyweight dominance in the world today.