Michael Phelps hints at return for Rio 2016 Olympics

Michael Phelps has suggested that he may return to professional swimming for the Rio Olympic Games in 2016.

The 28-year-old announced his retirement from the sport at the end of the London 2012 Games, where he became the most successful athlete in Olympic history.

"I don't know what's going to happen in the future," Phelps reportedly told The AP during the World Swimming Championships in Barcelona. "I don't know what's going to happen tomorrow."

Phelps picked up 22 Olympic medals in his career.