When all-time great Floyd Mayweather takes on pro debuting novice Conor McGregor, the UFC star immensely familiar with fighting but not boxing, most agree on one aspect of the fight: For the "Notorious" one to win, he is going to have to score a knockout.
Mayweather (49-0, 26 KOs) is a master boxer and perhaps the greatest defensive fighter of all time, so should McGregor land that big punch and win, many will consider it the biggest upset in sports history.
Throughout his 21-year professional career, Mayweather has rarely been hit cleanly and has only been knocked down once officially, so there are many who believe the result of the 12-round junior middleweight bout on Saturday (9 Showtime PPV, 9 p.