Possible comeback for Michael PhelpsTo view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 videoUli Riedel11/17/2013November 17, 2013The Olympic swimming champion has rejoined the US Anti-Doping Agency's drug testing program - a pre-requisite for competing in professional sports. He could now take part in next year's US championships.https://p.dw.com/p/1AJ40Advertisement