Floyd Mayweather Jr. plans to go out unbeaten and on his own terms, as 'The Best Ever', when he ends his boxing career in Las Vegas next week with a welterweight title defense against Andre Berto.

Should Mayweather win, as is widely expected, he would match the 49-0 record of former heavyweight great Rocky Marciano but says he wouldn't be tempted to come out of retirement for a 50th fight.

"Forty-nine is my last fight," the five-division world champion, aged 38, told reporters on a conference call on Wednesday, before saying that self-preservation in the ring had always been a top priority.