Floyd Mayweather Jr has claimed that remaining undefeated gives him a psychological edge over Manny Pacquiao going into Saturday's superfight.
The American has won all 47 of his professional bouts, while Pacquiao has lost five times during a 64-fight career in which he has become the first ever eight-weight world champion.
Mayweather has claimed that will create doubt in the Filipino's mind ahead of their lucrative and long-awaited meeting in Las Vegas.
"I've never been defeated. I don't know what it means or feels like to lose. But once a boxer experiences that the doubt will always be in his mind," Mayweather told reporters at the MGM Grand on Wednesday.
Pacquiao lost consecutively to Timothy Bradley and Juan Manuel Marquez in 2012.
