Here's a look at six fights that have defined Mayweather's career. — Tim Dahlberg, AP Boxing Writer
Officially this goes into the books as Mayweather's last loss, though it would be hard to find anyone outside Bulgaria who thought Serafim Todorov won his 125-pound semifinal against Mayweather in the 1996 Olympics in Atlanta. Even the referee thought Mayweather won, raising his arm instinctively as the 10-9 decision in favor of the Bulgarian two-time world champion was announced. Mayweather didn't help his own cause by not throwing a punch in the final 15 seconds, and had to settle for the bronze medal. It was a mistake he would not repeat as a pro. "They say he was the world champion," Mayweather said. "Well, we know who the real champion is."