The emergence of US sprint star Tyson Gay has left Jamaica's 100m world record-holder Asafa Powell looking suddenly vulnerable at the Osaka championships.
Gay has set the track alight this season, scorching to the leading time of 9.84 seconds and placing a big question-mark over Powell's bid for an elusive first world crown.
Powell, by contrast, has struggled with knee tendinitis and an untimely groin injury, timing 10.04 seconds in his final warm-up in Stockholm.
"I am unbeaten, he is unbeaten and one of us is going to lose in Osaka," said the confident Gay.
While the showdown has fans licking their lips it is an unexpected challenge for Powell, the only drug-free man in history to run 9.77 seconds, who has a nasty habit of fluffing his lines on the big stage.
Powell false-started his way out of the 2003 world championships, and a year later the easy-going Jamaican disappointed everyone when he failed to get out of the blocks in the Athens Olympic final.
"It wasn't the race I expected," he said afterwards.
But Powell returned to the Olympic stadium in June 2005 to set his world-record 9.77 -- a performance emulated only by Olympic and world champion Justin Gatlin, who has since failed a dope test.
Powell missed the 2005 worlds with a torn groin muscle, and flirted with disaster before winning last year's Commonwealth title by veering into a competitor's lane in the semifinals.
Now, one year from the Beijing Olympics, the 24-year-old will be keen to lay the big-day demons to rest with the most important title of his career.
Gold for the preacher's son would be a popular outcome, with Powell seen as a beacon of fair play in a sport increasingly tainted by drug scandals.
"I'm Jamaican-born, grew up in the church and there is nothing unfair about me," he has said. "I'm just trying to keep it that way."
Powell was born in St. Catherine, Jamaica apparently with natural confidence, predicting he would be the world's fastest man in his high-school yearbook.
Although his favourite sport was football he eventually followed in the footsteps of his brother, Donovan, a 100m world semifinalist in 1999.
"I didn't even like running. It was just running. I didn't know you could be a runner. I knew you could be a footballer. You went out and trained. You could be on a team," he said.
Tragedy struck in June 2002 when his brother Michael was shot dead as he drove a taxi cab in New York. Twelve months later another brother, Vaun, collapsed and died while playing football.
But in 2004 Powell, who has snubbed training stints in the United States for low-tech Jamaica, ran below 10 seconds for the first time in Kingston. He repeated the feat a dozen times in 2006 alone.
Last year was Powell's most successful yet, remaining unbeaten as he twice equalled his record, won the Commonwealth title and swept all six Golden League events, earning the accolade of IAAF male athlete of the season.