By Edward Chaykovsky

WBA/WBC welterweight champion Floyd Mayweather Jr. announced on the social networks that he's officially started his training camp for what is being billed as the "final fight" of his pro career on September 12th at the MGM Grand in Las Vegas.

But Mayweather's opponent is still unknown. In 2013 and 2014, Mayweather fought twice - on Cinco De Mayo weekend in May and Mexican Independence Day weekend in September.

In the last two years, his September opponents were announced well in advance.

We are now at the mid-way point and Floyd's next opponent is still unknown issue.

Last month Mayweather named Andre Berto and Karim Mayfield as the two frontrunners. Most believe the two names are being used as a smokescreen for the real opponent.

Some still view Amir Khan as the frontrunner to land the fight. But Khan says there is no update regarding the fight - and both boxers share Al Haymon as their career adviser.

If the rumors prove true, and Mayweather actually steps away from a pay-per-view platform for the first time in ten years in order to fight on CBS - then a fight with Berto or Mayfield is certainly a possibility. But Berto and Mayfield are also in the dark on Mayweather's decision for September.

The long-shots to land the fight would be WBA 'regular' champion Keith Thurman, IBF champion Kell Brook and former beltholder Shawn Porter.