Wayde van Niekerk was one of the great stories of Rio 2016, stunning the world with his record time of 43.03 as he won gold in the 400 metres.
The South African was back on the track on Sunday morning in Tokyo, and he has some work to do if he wants to get back to the medal stand five years later.
Van Niekerk finished third in his heat to qualify for the semi-finals, but his time of 45.25 seconds ranked as the 12th-fastest among all competitors.
"I definitely came with a bit of nerves but I think I handled it well," he said. "I took it by my stride, switched off a bit too soon, but still got the job done."
USA's Michael Cherry had the leading time at 44.82, while the top two finishers in Van Niekerk's heat, Colombia's Anthony Zambrano (44.87) and Steven Solomon (44.94) of Australia, were both among the fastest four athletes.
After his heat, Van Niekerk sounded like a man adjusting to his new reality, as he will not sneak up on anyone this time.
"Walking around again, looking at [the] Olympic record and world record and that's my time, it sometimes feels a bit unreal," he said. "But this time around it’s a new championship, new rounds. I have to totally focus on the mission right now."
In the only medal event of the morning at the Olympic Stadium, China's Gong Lijiao took gold in the women's shot put with a throw of 20.58m, with USA's Raven Saunders second at 19.79m.
But Valerie Adams' bronze medal at 19.62m may have been the most impressive achievement, as the 36-year-old medalled in the event for the fourth consecutive Olympics.
After finishing seventh at Athens 2004, Adams won gold in Beijing and London before taking silver in Rio. She is now the only woman in history to medal in the same field event four times.
Shot put for @ValerieAdams84— World Athletics (@WorldAthletics) August 1, 2021
She wins her fourth #Olympics medal and becomes the only woman in history to achieve the feat in a single field event.
Rio 2016: #Tokyo2020 : pic.twitter.com/W2vYqjNFVY
WORTHINGTON TAKES BMX FREESTYLE GOLD
Charlotte Worthington won the BMX freestyle park event Sunday, making Great Britain the first nation to take gold in all five Olympic cycling disciplines.
The 25-year-old from Manchester fell on her first run in the final but landed the first-ever 360 backflip in competition on her second to score a 97.50.
Hannah Roberts of the USA took silver with a 96.10 on her first run before falling on her second and Nikita Ducarroz of Switzerland claimed bronze with an 89.20.
“I'm over the moon," Worthington said. "I’m still sitting here waiting to wake up. I’ve been thinking about this day for the past three or four years, just going in and out of thinking I can, or I can’t do it.
"I’m literally waiting to wake up right now. It feels like a dream.”
Australia's Logan Martin took the first men's gold medal in the event, his 93.30 on the first run getting the better of Venezuela's Daniel Dhers (92.05) and Great Britain's Declan Brooks (90.80).
FIRST MEDAL AT LAST FOR FRATUS
Amid more history-making performances for the American men and Australian women on the final day of swimming competition, Brazil's Bruno Fatus achieved some long-awaited personal glory.
The 32-year-old took bronze in the 50m freestyle behind Caeleb Dressel of the USA and Florent Manaudou of France, his first Olympic medal in his third attempt.
A three-time world championships medallist in the 50m free, Fratus finished an agonising 0.02 seconds off the podium at London 2012, then placed sixth in the event four years later in Rio.
On Sunday, he ascended to the podium at last.
"Winning bronze releases a lot of pressure that was on my back," Fratus said. "I’m so pleased to step on the podium with Caeleb and Florent, two of the best swimmers in history.
"Caeleb has all the potential to beat Michael Phelps’ (records) one day, who knows?
"And Florent is a beast, a monster and one of the best in history. I’m proud to be his friend and share an Olympic podium with him."
Dressel won gold in the 4x100m medley too to reach five Olympic titles in Tokyo, while Australian Emma McKeon also did the 50m free and medley relay double to complete a haul of four gold medals and seven medals in all for the Games. She equalled the haul of gymnast Maria Gorokhovskaya at Helsinki in 1952 – the most won by any woman in one Olympics.
IRELAND BOXER WITHDRAWS FROM SEMI-FINAL
Ireland's Aidan Walsh was forced to withdraw from his welterweight semi-final bout against Great Britain's Pat McCormack due to an ankle injury suffered in the quarter-finals.
McCormack moves on to fight for gold against the winner of the other semi between Cuba's Roniel Iglesias and Andrei Zamkovoi of the Russian Olympic Committee.
Walsh will leave Tokyo with a bronze medal and the praise of Ireland's boxing team leader Bernard Dunne.
"What Aidan did this week is an incredible achievement," Dunne said in a statement. "His performance throughout the tournament has been outstanding.
"It is great to see him write his name in the annals of Irish sport. Just over two years ago we selected Aidan for his first major championship, and over the past few months that potential that we had identified has grown and developed into a world-class performance, that reflects greatly on the level of preparation he has put in ahead of these Games."
Walsh's older sister Michaela also fought in Tokyo, falling Monday in the featherweight round of 16.