LONDON -- You should have been there.
You should have been there, at the Bird's Nest Stadium in Beijing, when Usain Bolt, with the stride of a colossus and the mien of a child, ran faster than any human ever had.
When Jamaica's Bolt won the 100- and 200-meter sprints on those humid nights four years ago in China, he mugged for the cameras before reaching the finish line, then mugged some more once he crossed, imitating an archer and revealing that he ate chicken nuggets before the race.
Bolt followed his worldwide unveiling by lowering his records in the 100 and 200 to 9.58 seconds and 19.19 seconds at the 2009 world track and field championships. He seemed momentarily untouchable, until the realities of the sport began weighing on him like cement shoes.
His back began to trouble him. His starts, never a strength, became a more pronounced problem, and he false-started at the 2011 world championships after his Jamaican teammate and training partner, Yohan Blake, flinched in the blocks.
With Bolt disqualified, Blake went on to win that race. This Olympics will establish whether that result was omen or aberration, whether Bolt's problems will prove inconsequential or career-changing.
The showdowns between Bolt and Blake will be centerpiece events in the London Games' track and field competition, which begins Friday.
Bolt calls Blake "The Beast.'' Where Bolt is fun-loving and unpredictable, Blake is a grinder who favors clichs and calm. The closest Blake has come to signaling his arrival at this Olympics was wearing a T-shirt reading "Eat My Dust'' at one of his sponsor's events.
But where Blake is the latest prototypical sprinter who could win a medal, like the United States' Tyson Gay, Bolt at his best is transcendent, the rare tall sprinter who runs with the same pace as a smaller man.
"I don't really say he's vulnerable," Gay said of Bolt. "But he's the only guy that's been where we haven't been. He's the Olympic champion. He knows what it takes.''
Blake, 22, beat Bolt, 25, in the 100 and 200 at the Jamaican Olympic trials, but for all of his problems, Bolt has run three of the fastest 100 times in the world this year. And while no one knows how Blake will handle the pressure of the Olympics, Bolt revels in the attention. The 100 final is Sunday, while the 200 final is Thursday.
"It's all about the championship,'' Bolt said in London. "I'm ready to go.''
He also called his losses to Blake "a wakeup call,'' leading Bolt to spend more time refining his start.
Former U.S. decathlete Dan O'Brien, in London working for Yahoo! Sports, knows how nerves can affect even the greatest athletes. A favorite to win a gold medal in 1992, he failed to qualify for the Olympics. He would win the gold in 1996.
"I look at track and field as a measuring stick for what human beings are athletically capable of,'' he said at the USA track team's practice at Mile End Stadium. "How high can we jump, how fast can we run? When I was young, I couldn't wait for it to be my turn, and when it was my turn, I couldn't wait for it to be over because it was so pressure-packed. And then when you're done, you can't wait to do it again. It's a thrill, but it's high pressure.''
Gay knows that all too well. He felt nervous long before track began in London. So much can go wrong in a short sprint -- a false start or bad start, not to mention a misstep, can mean the difference in a tenth of a second, the difference between gold and nothing.
"I'm feeling nervous," he said. "This is it. This is the big show. I tried to cram a lot of workouts in and a lot of weights in the least amount of time I could. I had to do everything I could, and it just came up on me real quick.''
Blake, who is 5-11, said Sunday's final would meet expectations. But there was no sense trying to intimidate anyone with gamesmanship at the start.
Gay could win, but the eyes of the world will be on Bolt and The Beast, who said of his quiet demeanor: "I don't need to scare the other athletes. When I'm running, I will scare them."
The New York Times and other news services contributed to this report.