By Kenneth Friedman: Floyd Mayweather Jr. is posting on social media his training for what some fans believe is going to be a comeback against either Conor McGregor or Khabib Nurmagomedov in 2020 or 2021. Mayweather hasn’t trained with this kind of consistent basis since he beat McGregor in 2017. The effort that the former five-division world champion Mayweather is ...