Superstar gymnast Simone Biles pulled out of a second event to protect her mental health on Wednesday, putting the spotlight on athletes' wellbeing at a Tokyo Olympics held under strict rules to prevent the spread of coronavirus.
Biles, who caused shockwaves with her withdrawal during the team event on Tuesday, also ditched the all-around, raising doubts about her further participation in Tokyo.
They overshadowed another busy day at the delayed 2020 Games, where US swimming great Katie Ledecky bounced back from her second defeat by Australia's Ariarne Titmus to win her first gold in Tokyo.
Elsewhere Ledecky, who won four gold medals at the Rio 2016 Games, lost her 200m freestyle crown to Titmus, two days after also ceding her 400m title to the Australian.
But Ledecky regrouped to annihilate the field in the first women's 1500m held at an Olympics, finishing more than four seconds clear of US teammate Erica Sullivan.
Ledecky, 24, is just the fourth female swimmer to claim six Olympic gold medals. However Titmus, nicknamed "Terminator", is emerging as one of the stars at the Tokyo Aquatics Centre.
Japan's Yui Ohashi completed a medley double, winning the 200m event to go with the 400m gold she secured on Sunday, while world record-holder Kristof Milak powered to the men's 200m butterfly gold.
Japanese gymnast Daiki Hashimoto won the coveted men's all-around title at the age of 19, edging China's Xiao Ruoteng with a superb final horizontal bar routine.
The United States made history as the first 3x3 basketball Olympic champions when their women beat the Russian Olympic Committee 18-15. Latvia took the men's title.