SEPTEMBER 10 (Reuters) — For Floyd Mayweather Jr., it was very familiar territory as he explained why he was the best boxer of his generation during the buildup to what he says will be the final bout of his career against Andre Berto on Saturday. The five-division world champion will put his unbeaten record on the line when he defends his WBC and WBA welterweight titles against fellow American Berto at the MGM Grand Garden […]