Sydney, Mar 9 (AFP) Disgraced Chinese swimmer Sun Yang's veteran coach Denis Cotterell has severed all ties with the three-time Olympic champion after his eight-year drug ban, Australian media reported.

Australian Cotterell, regarded as one of the world's top coaches, had worked with the freestyle specialist since the 2008 Beijing Olympics and long maintained Sun was clean.

But after the Court of Arbitration for Sport (CAS) banned Sun last month for refusing to give a doping sample in September 2018, Cotterell said he was now "retired".

"I have terminated my contract with (the) Chinese Swimming Association," he told the Sydney Daily Telegraph on Sunday.

Sun insists he is innocent and is to appeal, with his lawyer reasserting his defence that doping officials who came to his home were not qualified or authorised, and it was they who decided not to pursue testing.

Asked if he supported Yang's appeal, Cotterell replied: "No." It was the 28-year-old's second ban for doping, having served three months in 2014.

Nevertheless, Cotterell told AFP at the world championships in South Korea last year: "He's not a drug cheat.

"You can't have the performances he's had over the years without doing the work. He's been tested year in, year out -- hundreds of tests, winning every year over this period of 10 years."

A vial of Sun's blood was smashed with a hammer during the contentious testing session in 2018, but he was originally acquitted of anti-doping violations by world swimming's governing body FINA who agreed that testers had failed to produce adequate identification.

The World Anti-Doping Agency took the matter to CAS, demanding a ban of between two and eight years for missing the out-of-competition test. (AFP)

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