Irish record holder Joanne Cuddihy was disqualified from Sunday's World Championships 400 metres semi-finals in South Korea for a false start.
The Kilkenny woman had qualified by coming third in her heat on Saturday in a season's best of 51.82 seconds.
She finished behind former World Championship bronze medallist Novlene Williams-Mills and three-time 200m champion Allyson Felix.
"I can't blame anyone but myself for the false start," said Cuddihy.
Later in the championships, Cuddihy will run in the 400 metres relay with team-mates Claire Bergin, Michelle Carey and Jessie Barr.
Britain's Olympic champion Christine Ohuruogu was disqualified for a false start in the 400m heats.