Pacquiao is 32 years old, Mayweather is 34, and the Klitschko brothers and Sergio Martinez are all on the wrong side of 35. In the not too distant future, these great fighters will become memories in the ring. Their legacies will be debated as new fighters move into the spotlight.
Ten years from now, who will be on top of the boxing mountain? It's impossible to say, but the fighters on this list have a head start towards greatness. All aged 25 or less, they've already displayed skills that may turn them into future pound-for-pound contenders.
Some will rise to the top, some will drop off as they continue to campaign. Undoubtedly, some youngster not on this list will bloom later into a great champion.
Boxing is a generational sport. This new generation may be better than the last or they may not. In either case, the six men on this list have shown the sparks that define future champions.