Nick Kyrgios' return to the Australian Open is over after he and partner Thanasi Kokkinakis stopped playing while trailing in the second set of their first-round doubles match.

A seething Thanasi Kokkinakis has described his ongoing pectoral muscle issues as “physical and mental torture” after losing a five-set epic at the Australian Open.

World No 1 Jannik Sinner makes it 16 wins in a row; No 5 seed Daniil Medvedev dumped out of Australian Open by 19-year-old American Learner Tien in five-set epic; Nick Kyrgios and Thanasi Kokkinakis p

Kokkinakis was forced to withdraw from the Adelaide International last week due to a shoulder injury, and his chances of a first-round win at the Australian Open looked dire. It led Aussie legend Woodbridge to question whether Kokkinakis should have been prioritising rest in the lead-up instead of playing exhibition events for the money.

Nick Kyrgios and Thanasi Kokkinakis's bid to repeat their Australian Open doubles triumph of 2022 ended in retirement in on Thursday when the latter was unable to continue their first-round tie.

Thanasi Kokkinakis concedes his debilitating pectoral muscle injury will likely force him to pull out of his hotly-anticipated 'Special Ks' doubles reunion with Nick Kyrgios. While Alex de Minaur will headline the Australians in action on Thursday,