The withdrawal of Jamaica's Asafa Powell from the 100m at the World athletics championships has left compatriot Usain Bolt an even stronger favourite to add to his glittering collection of medals.
Powell, the fastest man in the world this season over the short sprint (9.78sec), and Bolt's biggest rival for gold, was forced to pull out of the blue riband event after failing to recover from a niggling groin injury.
Also missing from the Korean showdown are American Tyson Gay, the second fastest man in the world this year, and Jamaican Steve Mullings, the third quickest, who misses the worlds after a failed drugs test.
Even in a full-strength field, Olympic and World champion Bolt would have been hot favourite to win on the big stage but it is now difficult to see where the challenge will come from for the World record-holder.
But Bolt himself, who is well down the list of the world's fastest times this year with 9.88sec, has played down expectations that he will be in World record-breaking form, saying he is battling back to his best.
“This for me is a comeback season from injury. I have been working really hard this season to get back in tip-top shape,” said Bolt, the sport's headline act.
After storming to the 100m and 200m sprint double in then-World record times at the 2008 Olympics, Bolt repeated the trick a year later, setting new marks of 9.58 and 19.19sec. He also won the 4x100m relay at both events.
Injury lay-off
But an injury lay-off looks to have ended hopes to go even faster at the worlds in South Korea, which starts on Saturday, when Bolt will run in the 100m heats, with the final held on Sunday evening.
The sprinter said the challenge had been in getting back into shape and honing his technique, adding: “I wouldn't say it's 100 per cent but I'm happy with where it is and I'm going out there to do my best.”
Other Jamaican sprinters to look out for include Yohan Blake, Bolt's training partner, and Michael Frater.
The U.S. team includes national champion Walter Dix and former Olympic champion Justin Gatlin, who returned to the track this season after a four-year suspension, although he is reportedly suffering from frostbite after treatment in a cryogenic chamber with wet socks.
Lemaitre leads challenge
Europe's challenge will be led by Christophe Lemaitre, who won Euro gold in the 100m, 200m and 4x100m relay in Barcelona last summer, though he believes the 200m is more realistic for a podium finish.
“Jamaica can afford to replace him (Powell) with Michael Frater. And given the strength in depth there is on the 100m, it still remains tight,” he said.
Also in action on the opening day in South Korea is three-time defending World 200m women's champion Allyson Felix, who goes in heats of the 400m in her bid for a memorable double.
Felix has reigning World champion and fellow American Sanya Richards-Ross in her sights, although the latter put months of strife aside in storming to victory at the London Diamond League earlier this month in an impressive 49.66sec.
Jamaican trio Rosemarie Whyte, Novlene Williams-Mills and 2009 Berlin worlds silver medallist Shericka Williams will also be in the running along with Botswana's Amantle Montsho.
The semifinals of the women's 400m will be run on Sunday, with the final scheduled a day later.
Rudisha in good form
Kenyan World record-holder David Rudisha will open his campaign in the heats of the men's 800m, looking for an easy ride through to Sunday's semifinals before the final on Tuesday.
There are just two medal events on the first day of competition at the nine-day worlds, in the women's 10,000m and marathon.
The latter event will be raced around a multi-lap (2x15km, 1x12.195km), largely flat street circuit. In the absence of defending champion Xue Bai of China, compatriots Zhou Chunxiu and Zhu Xiaolin, Asian Games champion and silver medallist respectively, will lead the way.
Yoshimo Ozaki and Aselefech Mergia, defending World silver and bronze medallists, head up the Japan and Ethiopia teams, while Kenya will be led by London marathon third place-getter Edna Kiplagat, whose 2:20:46 makes her the fastest entrant in the field.
In the 10,000m, Ethiopian Meseret Defar will compete in her bid for a 5000-10,000m double, and will have Kenyan Vivian Cheruiyot, defending World champion at 5000m, in direct competition in the two events.
Another Kenyan, Linet Masai, the defending 10,000m champion, is also in the running.
The opening day also sees the first half of the decathlon, with the United States' high hopes of a strong podium showing falling on the shoulders of world leader Ashton Eaton and defending World champion Trey Hardee.
