Usain Bolt will aim to do what no other athlete has ever been able to do before in Rio when he bids to win a third successive Olympic 100 metres title.
The Jamaican has never cracked under that sort of pressure before, although this time has had to overcome a hamstring problem that prevented him from running in the final of his national championships at the start of July.
He returned to run in the 200m at the Anniversary games in London on July 22 - when he eased himself back - but at the moment he is only the fourth quickest man over 100m this year. Here are his threats in the blue ribband 100m event in Rio.
Justin Gatlin - United States
2016 fastest time: 9.80 in Eugene, US, July 3
The 34-year-old American is the man most likely to beat Bolt and earlier this year he did beat the Jamaican's 100m world-record time of 9.58 seconds by a whopping 0.13secs. Okay, that time was set while appearing on a Japanese TV show, and he did have the aid of some massive fans to push him along, but hey, it was still quick.
Gatlin's best legitimate time this year is the fastest in the world so far and he was the 100m Olympic champion in 2004. He has, however, twice been banned for drugs and that hangs heavy over him every time he takes to the track.
Yohan Blake - Jamaica
2016 fastest time: 9.94 in Kingston, Jamaica, June 11
Blake won the Jamaican Olympic trials last month in the absence of Usain Bolt in a time of 9.95secs, although his coach Glen Mills warned him afterwards that he needs to up his game ahead of Rio. The time was slower the his season-best, when he was easily beaten by Bolt and Nick Ashmeade, but the silver medallist from London 2012 has said he can step up when it counts.
Trayvon Bromell - United States
2016 fastest time: 9.84 in Eugene, US, July 3
Bromell is the up-and-coming star of in the sprint world. The 21-year-old clocked the third fastest time of the year as he narrowly finished second to Gatlin in Eugene. He has already shown he can handle the pressure of a big event too after he tied for a bronze medal at last year's World Championships in Beijing.
Jimmy Vicaut - France
2016 fastest time: 9.86 in Paris, June 7
The Frenchman clocked his personal best earlier this year in Paris - to equal the European record over 100m - after he had almost pulled out of the race with a tight right hamstring. Vicaut went just as quickly last year only to have a disappointing World Championships where he only qualified for the final as the equal eighth-quickest before finishing second-to-last in the medal race in a time of 10 secs flat.
Akani Simbine - South Africa
2016 fastest time: 9.89 in Szekesfehervar, Hungary, July 18
The young South African has been dubbed 'the next Bolt' - a rather hefty tag after he failed even to reach the Commonwealth Games final two years ago. He has emerged since and last month thrust himself into medal calculations when he beat Jamaican Asafa Powell in Hungary in a personal best of 9.89 secs. That time also broke the South African record for 100m. The 22-year-old had dreamed of playing for the Bafana Bafana before being pushed onto the track.
Andre De Grasse - Canada
2016 fastest time: 9.99 in Edmonton, Canada, May 29
The tattooed Canadian burst onto the world stage last year as he claimed a bronze medal at the World Championships. This year he has not been able to replicate anything near the times he clocked last season - getting back to full health after moving his training to Phoenix - although his coach Stuart McMillan has billed him as a "big-time competitor" who steps up on the big stage. Former Canadian Olympic 100m champion Donovan Bailey is a fan while De Grasse showed he's returning to peak for wining the Canadian Olympic trials in a season-best time of 9.99 secs.
James Dasaolu - Great Britain
2016 fastest time: 9.93 in Birmingham, England, June 25
Dasaolu is probably Great Britain's best hope in the 100m, albeit without firm hope of testing the podium places. He won in Birmingham in June when three British men ran under 10secs in the same race for the first time ever - he beat out James Ellington or CJ Ujah in a time of 9.93secs that was aided by a +3.0 tailwind. Reaching the 100m final would be a major prize in Rio and, just perhaps, the 4x100m replay could bring something more significant.