Novak Djokovics lawyers filed court papers Saturday in his challenge against deportation from Australia that show the tennis star tested positive for COVID-19 last month and recovered, grounds he used in applying for a medical exemption to the countrys strict vaccination rules.

The No. 1-ranked Djokovic was denied entry at the Melbourne airport late Wednesday after border officials canceled his visa for failing to meet its entry requirement that all non-citizens be fully vaccinated for COVID-19.

Djokovic was given a medical exemption backed by the Victoria state government and Australian Open organizers on Jan. 1, based on information he supplied to two independent medical panels, and he was approved for a visa electronically.

But it has since emerged that the Victoria state medical exemption, allowed for people who tested positive for the coronavirus within the last six months, was deemed invalid by the federal border authorities.

Djokovic has been confined to an immigration detention hotel in Melbourne, where hes been preparing for the legal challenge against his visa cancellation in the Federal Circuit Court on Monday.

The Australian Open starts Jan. 17. Djokovic is the defending champion and has won the Australian Open mens singles title nine times. He has 20 Grand Slam singles title, a mens record he shares with Roger Federer and Rafael Nadal.