Swimming: Sun looks to shine but clouds still hang over Phelps

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They may be competing in Shanghai – beneath the striking arches of the Oriental Sports Center on the banks of the Huangpu River – but thoughts will be firmly focused on London.

A year out from the Olympics, the world's best, from the mighty Michael Phelps to Sun Yang, the sport's new sensation, will be using the World Championships to assess their readiness for 2012 – and keep a wary eye on their likeliest challengers.

"It is a good chance to get the swimmers ready [for London]," said Yao Zhengjie, the China coach, of the meeting that opens today. Phelps, the undoubted king of the pool in Beijing, has endured the worst spell of his career – he has been beaten three times in the 200m butterfly, an event he had not lost in for nine years – and will be closely watched to see if he is mortal after all. But it is Yang, the 6ft 5in teenager, who will be centre of attention, and not just because he is the poster boy for home hopes – which are high as China are a rising force in the sport.

At last year's Asian Games, the 19-year-old finished less than a second short of breaking the oldest record in the sport, Grant Hackett's 2001 mark in the 1500m. The great Australian dominated distance swimming but Yang appears to have the potential to extend his influence beyond that. He has recorded the fastest times in the world this year at 200m, 400m and 1500m. At the Chinese nationals this year, he destroyed the field in the 200m, a powerful kick conjuring a shattering turn of speed. He remains a work in progress – his turns can be ragged – but his contest with South Korea's Park Tae-hwan, the Beijing gold medallist, in the 400m, will be instructive of how good he can be.

Phelps won five golds in the last World Championships in Rome in 2009, to follow his eight in Beijing, and admits he lost his edge afterwards and there were times that he had to be dragged "kicking and screaming" to training. He also suffered a 400m individual medley defeat this year, but now claims to have rediscovered his desire. "I feel a lot better," said the 26-year-old. "It's like the old feeling I used to get leading up to meets."

Britain's first interest comes with Tom Daley and Pete Waterfield in the 10m synchronised diving tomorrow. Daley is also defending the 10m platform title he won two years ago.