The highly anticipated return of Floyd Mayweather Jr. has been postponed for the time being, due to an injury that will keep the boxer from training.

According to reports, the 32-year-old former boxing champ damaged cartilage in his ribs and had to stop training for his comeback fight until a doctor says he can resume.

"He tried to work through it. He really did not want to postpone the fight, but it came to the point where he could barely sit," Richard Schaefer, of Golden Boy promotions, told the Associated Press. "He could not train, he could not move and there was really not much of a choice."

The undefeated Mayweather was scheduled to fight Juan Manuel Marquez on July 18 at the MGM Grand in Las Vegas, but things will be pushed back due to the injury.

Schaefer told the AP that both fighters have committed to rescheduling and a September date has been mentioned. But promoters and the fighters won't agree to a date without the OK of doctors.

Mayweather's ribs are not broken, and he plans to see a doctor this week. How he damaged his ribs is currently unknown.

"Right now he cannot go and train, he cannot work out, he cannot run, he cannot hit the heavy bag and the speed bags and jump ropes and all these kinds of things," Schaefer explained. "He definitely will need some additional training, but again, Floyd is such an amazing athlete -- and really on top of his game -- that I think it will be relatively easy for him to get right back into it."

Cartilage connects the ribs to the sternum, and can tear away after direct blows to the chest, other trauma or particularly violent coughs and sneezes.

Mayweather hasn't boxed since knocking out Ricky Hatton in December 2007. He was slated to fight a rematch with Oscar De La Hoya, but instead abruptly retired last June, while still considered the sport's pound-for-pound king.

While absent, Filipino fighter Manny Pacquiao took the best pound-for-pound title, after beating both De La Hoya and Hatton in fewer rounds than Mayweather.

Mayweather's fight against Marquez could possibly lead to a meeting against Pacquiao in the near future, if he wins of course.

Stay tuned for updates at a later time.