Imagine if, at the men's 100 metres final on Sunday evening, Usain Bolt does what he did at the world championships last year and mis-judges the start. If he leaves the blocks before the gun goes, that will be it: he will be out.
Now imagine how you would feel if you were fortunate enough to have a ticket for the London Games' showpiece event. Imagine the atmosphere in a stadium that has been tingling with anticipation in the hours leading up to it. It would suddenly become flatter than a cricket pitch.
Such a phenomenon, albeit on a smaller scale, in front of 6,000 rather than 80,000 people, was witnessed in the new velodrome on Thursday when the British team of Victoria Pendleton and Jess Varnish were put out of the team sprint for infringing an arcane rule, which later saw the winners, China, relegated to second place for the same violation.
It's a phenomenal crowd and I'm just really devastated that we've disappointed all the people that have come to support us. I think they would've loved to have seen us up there.
Quotes of the week
The events in the velodrome continued a disturbing trend at these Olympics: one that seems to have been caused by governing bodies tinkering with their rules for no obvious benefit. We saw it in the badminton, too, when eight players were sent home for throwing matches.
That was wrong, clearly, and it short-changed those who had paid for tickets to see them play, but the four doubles pairings were not throwing matches for financial gain or on behalf of some betting syndicate. They were trying to give themselves a better chance of winning a medal by gaining an easier draw in the next round, after the (new) group stage of the tournament.
The group stage is an innovation by the Badminton World Federation to give more matches and exposure to 'new' countries. Perhaps that should mean the federation should bear some responsibility for the players' actions. After all, there is much at stake for the players; they are professionals, not amateurs, so can they really be expected to follow Corinthian ideals?
For 'countries,' by the way, read 'markets.' Cycling's world governing body, the UCI, had the same motivation when they came up with a new rule that is also designed to open the sport up to 'new' countries.
This is the one rider per nation stipulation, which, it was hoped, would see track cycling take off in new places, and prevent a superpower such as Britain winning multiple medals and achieving one-twos, as they did in Beijing.
The result, however, is that many of the events are deprived of some of the sport's biggest stars. It means that Sir Chris Hoy, who won his fifth Olympic gold medal in the team sprint on Thursday evening, will be denied the chance to repeat his three gold medal-haul in Beijing and to defend his sprint title. It also means, as Hoy has said, that the Olympics is less competitive than the world championships, which doesn't seem right.
As for the rule that saw the British and Chinese teams relegated in the women's team sprint, it is one that has existed but not been enforced until the world championships in Melbourne in March this year, where Hoy and co were among the teams that fell foul.
It concerns the changeover: the moment when the rider who's following in the slipstream of their teammate hits the front. A bit like relays in athletics, there is a designated area for this.
But the rule seems pointless, because any advantage conferred by breaking it would appear to be negligible, if indeed there is an advantage.
There didn't seem to be any problem with the team sprint before this rule was enforced. But there was a problem on day one in the velodrome, because the two fastest teams, China and Britain, were penalised. They were deprived of the medals they should have had, and the paying fans were deprived of the spectacle they should have enjoyed.
In football they say that if you are not aware of the referee then he is having a good game. The same is true of any sport. In the velodrome on Thursday, the officials competed for attention with the riders. That's wrong. The UCI need to address it, but, when and if they do, it will be too late for the Chinese team, and too late for Pendleton and Varnish.
Let us hope that on Sunday, when a hush descends on the Olympic Stadium as the eight men's 100m finalists line up, the attention remains on them, not the officials.