Undefeated pound for pound champion Floyd Mayweather has officially started training for his September 12th fight at the MGM Grand in Las Vegas, NV. Mayweather posted a video of himself hitting bags and sparring the first day back. Mayweather has yet to announce an opponent for the fight though Amir Khan and Andre Berto appear to be the frontrunners. There is also a chance that Mayweather's final fight will not land on Showtime PPV, and could possibly be on CBS, though that is all speculation. No one has confirmed or denied it. Mayweather is expected to make an announcement soon on who the opponent will be.