Undefeated records have taken on an unhealthy value in contemporary boxing. Floyd Mayweather's perfect record is a remarkable historical achievement and makes him an obvious first-ballot Hall of Famer.
But it doesn't necessarily mean he deserves to rank above other great fighters from earlier eras, when boxers competed more frequently and every top guy fought every other top guy, often multiple times. In that kind of environment, losses were inevitable, no matter how great a fighter was.
Still, winning is the point of the contest. And no fighter wants to give up his zero.
Here's a look at when the top unbeaten stars in the sport today are likely to finally lose.