Floyd Mayweather Jr's uncle believes that the pound-for-pound king will not get credit unless he knocks out Manny Pacquiao in the ring in Las Vegas on Saturday.

Many have tipped the welterweight fight to go the distance, but Mayweather is favourite to come out on top as he is unbeaten in all of his 47 professional bouts.

However, Roger Mayweather, who is one of his nephew's trainers, believes that the American needs a knockout to improve his legacy.

"Every time somebody talks about the fight, 'oh, you know you're definitely going to have to knock out Pacquiao, otherwise, [Mayweather] ain't going to get no credit,' but that's part of boxing," worldboxingnews.net quotes Roger as saying.

"As good as Floyd is supposed to be, I don't think that they are going to give him the credit that he deserves [without a knockout]."

The fight will be held at the MGM Grand Garden Arena.