The coach of sprinter Justin Gatlin has stepped down as the head of the United States relay squads just months out from the Rio Olympics due to a change in USA Track and Field's criteria.
American sprinter Sha'Carri Richardson, expected to be one of the biggest draws at the Tokyo Olympics, will miss the 100 metres at the Games after accepting a one-month ban for testing positive for cannabis during her US trials victory in June.
World 100 metres champion Justin Gatlin said on Tuesday he is "shocked and surprised" at doping allegations made against his coach Dennis Mitchell, like Gatlin a convicted doper, but added that he sacked him as soon as he heard about the issue.