When the Games open on August 5 Usain Bolt .
Michael Phelps will be the undisputed headliners but when the Olympic flame is extinguished on August 21 it could be Biles leaving Brazil as the newest Olympic darling .
When the Games open on August 5 Usain Bolt and Michael Phelps will be the undisputed headliners but when the Olympic flame is extinguished on August 21 it could be Biles leaving Brazil as the newest Olympic darling .