Usain Bolt Already in London we have seen the dimming of one of sport's brightest bulbs. Now we wait to see if time and rivals have caught up to Usain Bolt like they have with Michael Phelps.
The heats of the 100m start tonight and what seemed like a foregone conclusion a year ago now shapes as the most fascinating event of the Olympics.
Bolt is the superstar, the man who four years ago changed sprinting forever; Yohan Blake is the young pretender, the reigning world champion and the first man who does not appear dazzled while in his compatriot's luminous presence.
At 8.50am on Monday NZT eight coiled springs will compress into their starting blocks and wait for the gun that will unleash them down a narrow lane for 100 metres.
All things being equal, if they cannot reach their destination in less than 9.9s, they can forget about a medal. If they cannot do it in less than 9.8s, chances are they can forget about gold.
It might well be the greatest field ever assembled for a 100m meeting - Tyson Gay, Asafa Powell and Justin Gatlin are other likely finalists - but most believe it will come down to a mano a mano duel between Usain "Lightning" Bolt versus Yohan "The Beast" Blake.
Bolt won gold in Beijing four years ago with an astonishing, foot-off-the-pedal 9.69s. If it seemed inconceivable that you could lop three-tenths of a second off the world record while showboating, then taking a further .11s off in Berlin the following year was ludicrous.
Bolt was a game changer. At 1.95m he was initially considered a 200m specialist because his long levers made him ungainly out of the starting blocks and ceded time to his squat, more explosive opponents (even discounting his false start shock at the world championships in Korea last year, the start is still the weakest part of Bolt's armoury).
But what he lacked in the first 5m he made up for in the second of sprinting's six phases, the drive. This is the phase where you drive your legs into the ground to straighten your body and work towards maximum stride length.
When he unfurls his stride at its fullest, nobody can match Bolt. It takes just 41 of them to get from A to B - most take 45.
"Last 10 metres, you're not going to catch me," Bolt said recently.
"No matter who you are, no matter what you're doing, no matter how focused you are, no matter how ready you think you are, you're not going to catch me, because that last 10 metres is going to take me three-and-a-half strides to pass the finish line."
But what if he's the chaser and not the chased?
When Bolt false-started himself out of gold in Daegu last year, there was a shockwave around the athletics world, but that was more for the fear a similar mistake 12 months later could rob the Olympics of its best scene stealer.
It didn't go unnoticed that Blake won, but it wasn't the story.
When Blake beat Bolt (not once, but twice!) at the Jamaican trials last month, he started forcing his way into the narrative, although the focus still remained on Bolt.
Reports emerged of a party lifestyle starting to take its toll, but Bolt insisted it was a hamstring injury, not late nights, slowing him down.
He flew to Munich to see high-profile sports doctor Hans-Wilhelm Muller-Wohlfahrt and then withdrew from the Monaco Diamond League meeting in what was meant to be his final pre-Games competitive outing.
All that has meant that one of the most famous people on the planet, the greatest sprinter of his generation and possibly the greatest athlete of all time, is coming to London as a bit of an unknown quantity.
But at least he has experience, right? "One thing I really hate is experience. Experience for me doesn't work," said Blake at his packed pre-Olympic press conference.
"Everybody's talking about experience this, experience that. For me it's all about going out there and keep focused and getting the job done." Every question about Bolt was fielded with the same, almost dismissive, response. It is all about executing well and not worrying about the man in the lane next to you, whether it be Bolt, Gay or the ghost of Jesse Owens.
"It's not about beating Usain or anyone else," Blake said.
In his eyes, maybe. In the eyes of the rest of the world, he could not be more wrong.
Age: 22 years
Fastest time: 9.75s
Strides it takes to cover 100m: 45
Age: 25 years
Fastest time: 9.58s (world record)
Strides it takes to cover 100m: 41