The much-anticipated 800-metres world championship freestyle clash between Australian swimmer Mack Horton and controversial Chinese star Sun Yang has fizzled out, with Horton failing on Tuesday to qualify for the final.

Horton, who created an international furore when he did not shake hands with Sun and refused to join him on the podium after being relegated to 400-metre silver by the 10-time world champion on Sunday night, managed only the 14th fastest time for Wednesday’s 800-metre final.

The stage appeared set for Horton and Sun’s bitter stoush to further escalate in the 800-metre freestyle final, with the pair considered medal chances.

But Horton’s disappointing heat meant he did not make the final eight.

Likely adding to his frustration, Sun was the eight-fastest qualifier. Australian Jack McLoughlin will also be in the mix: He had the third-fastest time in Tuesday’s heats in South Korea.

Horton said on Tuesday he would tone down his anti-doping stance at the Gwangju meet anyway “to protect the team” after receiving a FINA warning for his behaviour.

Facing the media for the first time since his protest, Horton initially avoided a question about his podium stance and instead spoke about the 800-metre freestyle heat.

“As much as I want to protect the sport, I still need to protect the team,” he said, when pressed.

“The focus now is the team’s performances and focusing on what everyone else is doing and making sure we get through the week.”

Horton’s feud with Sun erupted at the Rio Olympics, when the Australian dismissed the Chinese star as a “drug cheat” before claiming a shock 400-metre gold.

He has received death threats on social media for his stance in Gwanju.

Horton is unhappy that Sun, who served a 2014 doping ban, has been allowed to compete ahead of a Court of Arbitration for Sport hearing in September that might end the Chinese star’s career.

Sun has been accused of smashing vials of his blood with a hammer during a clash last year with testers.

He faces a lifetime ban if found guilty.

The China Daily led the country’s chorus of disapproval, saying: “Horton’s behaviour was not an insult to Chinese athletes, but an insult to himself.”

Vile messages have also inundated Horton’s Instagram page since Sun claimed the protest was disrespectful to China, with death threats directed at the Olympic champion, his family and even his girlfriend.

Horton has had support from other swimmers, including Italy’s 1500-metre Olympic champion Greg Paltrinieri, who is a good friend of the Australian.

“Not standing on the podium is a strong move. I don’t know if everybody would do that,” he said.

“But I need someone who does that …[and] Mack is the right person.

“The whole situation with Sun Yang happened like one year ago and we still don’t know anything [from FINA] … We need more transparency in this situation, so he [Horton] is right and I support him.”

Elsewhere, Australia’s Ariarne Titmus firmed as 200-metre freestyle favourite after three of the top four contenders pulled out of the world swim titles event on Tuesday.

Ariarne Titmus swims in her 200-metre freestyle heat. Photo: Getty

Australia’s world No.2 Emma McKeon and American great Katie Ledecky withdrew due to illness ahead of Tuesday’s heats. Canada’s Commonwealth Games 200-metre champion Taylor Ruck has been rested.

World No.1 Titmus, 18, has already claimed a shock 400-metre freestyle win after upsetting Ledecky on Sunday.

Australian officials said McKeon was rested for Tuesday’s 200-metre heats as a precaution but would still contest her remaining events – the 100-metre freestyle and four relays.

-with AAP