Britain's Mo Farah will bid to become the second man to achieve the double of the world and Olympics 5000 and 10000 metres titles while Usain Bolt begins his defence of the 200m on Friday at the World Athletics Championships.
Farah, who won an emotional double gold at the Olympics last year in the Somalia-born athlete's adopted home city of London, produced a courageous display to win the 10000m last Saturday and starts firm favourite to defend his 5000m title.
If successful he will emulate Ethiopian Kenenisa Bekele's double in 2009 which followed his victories in the 2008 Olympic Games.
Farah, whose American training partner Galen Rupp was a huge help to him in the 10000m and will again be in the field, admitted Sunday's race had taken more out of him than he had expected and just did the bare minimum to qualify for the final at the shorter distance.
"It's going to be a demanding race and I need as much energy as possible to have the reserves when the final kick comes," said the 30-year-old.
Farah, whose post 10000m race rubdown had to be improvised under a tree outside the stadium as security men would not allow him into the official area, said people shouldn't regard victory was his for the taking.
"I was getting texts from people just saying go and do it," said Farah.
"I'm like: it's not as easy as that. If it was, it would be boring. Seriously. If it was, everyone would be winning."
His chief opponents should be Kenyan duo Edwin Soi, the only athlete to beat Farah at the distance this year, and Olympic bronze medalist Thomas Longosiwa.
With both the Kenyans and Ethiopians likely to try and gang up on Farah, the Briton will once again be looking for the faithful Rupp to sacrifice himself in paving the way for him to take gold.
Bolt has kept a low profile since he powered to victory in Sunday's 100m final, regaining the title he lost when he was disqualified for a false start in Daegu two years ago.
The 26-year-old, world record holder in both the 100 and 200m, made up for that blip by retaining his 200m crown and there appears to be little in the way of opposition in barring his way to a third title in Moscow.
"I'm looking forward to running the 200m, I can't promise anything (regarding a new world record). Hopefully everything will come together," said Bolt.
Jamaica could well sweep the medals with Warren Weir looking to improve on his Olympic bronze from last year and Nickel Ashmeade hoping he can move up a notch after placing fifth in the 200m world final two years ago and the 100m final last Sunday.
While Bolt cannot break the record for world titles this week -- he can equal the present mark of eight of Carl Lewis and Michael Johnson -- that could fall on Friday to American great Allyson Felix.
Barring injury or a huge upset in Thursday's semi-finals, the 27-year-old -- who has three 200m and five relay golds -- will face Bolt's team-mate Shelly-Ann Fraser-Pryce, who like him regained her 100m title this week, in what could prove to be one of the most memorable clashes of the week.
Other finals will see Felix's veteran team-mate Dwight Phillips aim to win his fifth long jump title, 10 years after the 35-year-old won his first, although his form suggests he will be doing well to win a medal.
Were he to miss out on a medal it would be the first time in six appearances, the 2004 Olympic champion having taken bronze in 2007.
The men's shot put has Poland's two-time Olympic champion Tomasz Majezwski attempting to secure his first world title after four previous attempts with second his best showing in 2009.