They may not be perfect, but it would be hard to deny that Serena Williams, Tom Brady, Michael Phelps, Derek Jeter and Muhammad Ali are amongst the greatest athletes of all times. Whether they fight their battle on the tennis or basketball court, in a ring or on a field, they have proven time and time again that they deserve to be champions with their relentless dedication and incomparable contributions to their sport. These men and women have continued to inspire us -- aspiring champions and weekend warriors alike -- with their motivating words of wisdom.