Ailing Sun Yang's defence of his 1,500m freestyle Olympic gold foundered in the heats at Rio on Friday, where Michael Phelps remained the star attraction of the Olympic Aquatics Stadium.

Phelps, who took his tally of Olympic gold to 22 on Thursday with his fourth straight victory in the 200m individual medley, had a chance to make it four in a row in another individual event, the 100m butterfly, on Friday night.

In the last individual event of his spectacular Olympic career, Phelps will face a strong challenge from Singaporean Joseph Schooling, the top qualifier, as well as old rivals Laszlo Cseh of Hungary and Chad le Clos of South Africa.

In other finals on the penultimate day of swimming competition, Katie Ledecky seeks a fourth gold of the week in the 800m freestyle, the race that launched her to stardom at the 2012 London Games.

Hungary's Katinka Hosszu vies for a 200m backstroke title that with her 100m back and 200m and 400m medley victories would see her join Kristin Otto as the only women to win four individual swimming golds at one Games. France's World and Olympic champion Florent Manaudou leads the way into the 50m freestyle final.
But Sun and the China team marked the preliminaries. The  as he faded badly in the back half of the 1,500m to finish 16th overall in 15:01.97.

"I got a cold, didn't feel very comfortable," said Sun, who set the world record of 14:31.02 at the London Games. "Today my muscles felt very sore after 800 meters.

"People said I would pull out of the heats, but I stuck with it. The result is normal given my condition."

China was also under the spotlight after Chen Xinyi was suspended over failed doping test after finishing fourth in the women's 100m butterfly final on Saturday. She has asked for a second test on her sample and a hearing on the case.

Italy's Gregorio Paltrinieri, who won the world title in Russia last year when Sun, complaining of chest pain, pulled out of the final at the last minute, was taken aback by Sun's performance.

"It was a surprise," said Paltrinieri, who led the way into Saturday's final in 14:44.51. "Since last year when he missed the final we don't know what his condition is in the 1,500m. I feel sorry for him, but maybe his preparation was more for the 200 and the 400."

- US set up Phelps relay finale -

At the other end of the distance spectrum, Denmark's Pernille Blume clocked a personal best of 24.23sec to unexpectedly lead the way into the semi-finals of the women's 50m free.
She was just three-hundredths of a second faster than the 24.26 produced by Great Britain's Fran Halsall in the previous heat.

Aliaksandra Herasimenia of Belarus was third-quickest ahead of Australian Bronte Campbell. Campbell's elder sister Cate was seventh-fastest, both sisters out for redemption after disappointingly failing to medal in the 100m free.

London gold medallist Ranomi Kromowidjojo of the Netherlands tied for eighth-fastest while American Simone Manuel, who shared 100m free gold with Canadian Penny Oleksiak, advanced with the 11th-fastest time.

In the men's 4x100m medley relay heats, the US quartet of David Plummer, Kevin Cordes, Tom Shields and Caeleb Dressell did their job, winning their heat in the second-fastest time overall behind Great Britain to insure that Phelps will have a shot at one last gold in the final on Saturday.

"Got the job done, got the team through where they needed to be, got a good lane for tomorrow," said Plummer. "A DQ would have sucked."

The US women led the way into the final of their 4x100m medley relay ahead of Canada, Denmark, Russia and Australia.

Source: AFP