(AP) — Novak Djokovic’s 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 country’s strict vaccination rules.

The No. 1-ranked Djokovic was denied entry at the Melbourne airport late Wednesday after border officials cancelled 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 January 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 he’s been preparing for the legal challenge against his visa cancellation in the Federal Circuit Court on Monday.

The Australian Open starts a week from Monday on January 17. Djokovic is the defending champion and has won the Australian Open men’s singles title nine times. He has 20 Grand Slam singles title, a men’s record he shares with Roger Federer and Rafael Nadal.

The Australian Broadcasting Corp. and the Australian Associated Press reported details of the documents late Saturday, two days before the court hearing.

It showed Djokovic received a letter from Tennis Australia’s chief medical officer on December 30 last year “recording that he had been provided with a ‘medical exemption from COVID vaccination’ on the grounds that he had recently recovered from COVID.”

The exemption certification said the date of the 34-year-old Serb’s first positive test was December 16, 2021, “and that he had not had a fever or respiratory symptoms in the past 72 hours.”

On December 14, Djokovic attended a Euroleague basketball game between Red Star and Barcelona in a packed sports hall in Belgrade. He was photographed hugging several players of both teams, including some who soon later tested positive.

The court submission Saturday said Djokovic received confirmation from Australia’s Department of Home Affairs saying that his travel declaration had been assessed and that his responses indicated he met the requirements for quarantine-free arrival in Australia.

If he fails to have his visa cancellation overturned and gets deported, Djokovic could be barred from the country for up to three years.

Australian Open organisers have not commented publicly since Wednesday, except to tell Australian newspapers that no players have been misled over the vaccination requirements.