The Klitschko brothers have been dominating the heavyweight division for years.
While it seems that retirement will be on the horizon for 41-year-old Vitali Klitschko relatively soon, 36-year-old Wladimir Klitschko should remain a dominant fighter for several more years.
As long as Wladimir Klitschko is motivated to keep getting better and taking on the most worthy heavyweights, he should be a superb fighter.
While some critics refer to him as dull or lacking electricity when he steps in the ring, Klitschko does everything well, and he is starting to garner much greater respect from a historical perspective.
While nobody is about to say he belongs in a category with Joe Louis, Rocky Marciano or Muhammad Ali, he has highly developed skills.
The problem is finding worthy candidates for him or his brother that could provide significant challenges.
Here's a look at five heavyweights who could potentially challenge either of the Klitschko brothers.