Japanese gymnast Uchimura came into the Games hoping to add a fairytale final chapter to his Olympic career.
Instead, his Tokyo campaign became a horror story when the hometown favorite slipped off the horizontal bar on day one, failing to qualify for the final.
The 32-year-old had chosen not to defend the back-to-back all-around titles he won in 2012 and 2016 due to persistent shoulder problems, preferring to focusing on a single apparatus.
"In the last three Olympic Games I've been able to match the level of performance I'd reached in training –- but not this time," he said after the gamble backfired.
But a dejected Uchimura hinted he may delay retirement until after the world championships in Japan in October, giving him a chance to go out on a high.
Tokyo Olympics: Noah Lyles
The US sprinter who arrived in Japan heavily favored adding an Olympic gold medal to his 2019 world championship 200m crowns and lead a new generation of US speedsters tipped to dominate in the post-Usain Bolt era.
But the 24-year-old from Florida struggled to rediscover his best form during the 200m, narrowly avoiding a shock elimination in the semi-finals before being comprehensively defeated by Canada's Andre de Grasse in the final.
Tokyo Olympics: Trayvon Bromell
Lyles' teammate Bromell was the overwhelming favorite in the 100m heading into the Games after clocked the fastest time in the world this year with a blistering 9.77sec at a meeting in Florida in July.
But the 26-year-old looked off the pace from the outset in Tokyo, finishing fourth in his opening heat with a sluggish 10.05sec before being eliminated in the semi-finals after only managing 10.00.
Tokyo Olympics: Naomi Osaka
Osaka lit the Olympic cauldron to mark the opening of the Games but bid for glory failed to ignite on her return to tennis after a break for mental health reasons.
She crashed out in the third round after losing in straight sets to eventual silver medallist Marketa Vondrousova, saying the pressure of trying to win Japan's first tennis gold on her Olympic debut was "a bit much".
Tokyo Olympics: Kento Momota
Hometown expectations weighed heavily on badminton star Momota, a two-time world champion who entered the Tokyo Games as top seed after winning a record 11 titles in 2019.
The 26-year-old crashed out in the first round to an unseeded opponent, admitting he felt overwhelmed in the Olympic spotlight.
Swim star Daiya Seto hoped to defend his 400m and 200m medley titles in Tokyo but failed to make the final in the former and finished fourth in the latter.
Tokyo Olympics: Novak Djokovic
With the Australian Open, Roland Garros, and Wimbledon titles already in the bag, Djokovic came up short in his quest to become the first man to win a Golden Slam -- all four majors and Olympic gold in the same year.
Djokovic powered into the semi-finals and led Alexander Zverev by a set and a break before collapsing. He then self-destructed in a racquet-smashing bronze-medal defeat to Pablo Carreno Busta, before pulling out of the mixed doubles match for third place.
Tokyo Olympics: US women's football team
Driven by bitter memories of a 2016 quarter-final exit, the United States again arrived in Tokyo as gold-medal favorites seeking to become the first women's team to achieve the World Cup and Olympic double.
But a 3-0 loss to Sweden in their opening game snapped a 44-match unbeaten run and it never really clicked for a side still built around ageing stars Megan Rapinoe, Carli Lloyd, and Alex Morgan.
A first loss to Canada in 20 years in the semi-finals meant the Americans had to settle for bronze.