The United States, the reigning world champions and hot favourites for the inaugural Olympic 4x400m mixed relay, were on Friday disqualified from their heat after an erroneous baton changeover.
Their disqualification, for a first handover outside the permitted zone, deprives 35-year-old Allyson Felix of a chance to become the most decorated female athlete in track and field history.
Felix is currently tied with Jamaican legend Merlene Ottey with nine medals, a dazzling haul that includes six golds and three silvers.
Felix did not take part in the heat as Elija Godwin, Lynna Irby, Taylor Manson and Bryce Deadmon instead took to the track at the Olympic Stadium.
But Felix would no doubt have started the final on Saturday had the US made it through.
