The 22-year-old Nirmala clocked 53.07 seconds, well below her season's as well as personal best of 51.28, as she finished seventh in semifinals heat number two and 22nd overall out of total 24 competitors at the Olympic Stadium here.
Top two from each of the three semifinal heats and two fastest finishers from the remaining runners qualify for the final.
Bahrain's Salwa Eid Naser led the field going in the final with a 50.08 seconds effort while defending champion and Rio Olympics silver medallist Allyson Felix clocked the second fastest in 50,12.
Nirmala had yesterday finished fourth in her heat to qualify for the semifinals. She had taken the last spot among the six best finishers outside the automatic qualifiers.
"My target here was to do better than my personal best. But I could not do that without a personal coach. For an athlete in such a big event, a personal coach is very important. It is difficult without a personal coach," she added.
Disclaimer: No Business Standard Journalist was involved in creation of this content
