Wayde van Niekerk produced a truly remarkable performance on Sunday, to ensure Usain Bolt's history-making was not the only headline in Rio.
The great Usain Bolt has regularly brought gasps of amazement from crowds throughout his illustrious career.
Yet although athletics' biggest superstar added to his glittering CV with a historic third Olympic 100 metre title on Sunday, it was a different man who left spectators around the world utterly staggered by what they had just witnessed.
Wayde van Niekerk is the reigning world champion in the men's 400 metres, but both Kirani James and LaShawn Merritt - winners at the last two Olympics - were considered more likely to prevail on the grandest stage at Rio 2016.
It was surprising enough, therefore, to see Van Niekerk - running in lane eight as the fifth-fastest qualifier for the final - streaking clear down the home straight in the race that preceded Bolt's latest victory.
However, a bigger shock soon followed as the South African stopped the clock at 43.03 seconds, beating a world record set by American sprint king Michael Johnson 17 years ago.
If there was a sense of wonderment when Bolt lowered Johnson's apparently 'unbreakable' 200m mark in Beijing eight years ago, this was arguably a more sensational feat.
Prior to the Rio final, the quickest 400m of the year belonged to Merritt, who ran 43.97secs in the US trials.
With a third Olympic gold medal in his sights, Merritt went faster on Sunday with an impressive 43.85, while the classy James fared even better, registering 43.76 to improve on the time that brought him gold in London four years ago.
Neither man got remotely close to the champion.
Van Niekerk was already a hero in South Africa and made history earlier this year as the only athlete to break 10 seconds for 100m, 20 seconds for 200m and 44 seconds for 400m.
Nevertheless, few could have possibly imagined what the 24-year-old would achieve on Sunday.
While hugely significant in cementing Bolt's position as the greatest sprinter of all time, the 100m final did not provide the 'wow' factor of the Jamaican's most eye-catching triumphs, a winning time of 9.81secs relatively modest by his own exceptional standards.
However, those present in Rio's Olympic Stadium had already witnessed a true bolt from the blue - before Usain had even made it to the start line.