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 canceled his visa for failing to meet its entry requirement that all non-citizens be fully vaccinated against 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 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. 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.”

Djokovic attended a December 17 event in Belgrade honoring young tennis players. The event was covered by local media, and parents posted photos on social media showing Djokovic and the children not wearing masks. It’s not clear if Djokovic knew the results of his test at the time.

On December 14, Djokovic had 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.

So, who is at fault? Australian Prime Minister Scott Morrison tweeted “rules are rules” and that incoming passengers were responsible for meeting border regulations.

Tennis Australia and the government of Victoria state, where the Australian Open is played, are blaming confusion over the precise definitions regarding grounds for medical exemptions.

Tennis Australia, which runs the tournament and organizes the logistics for more than 2,000 incoming players, staff and officials, reportedly gave incorrect interpretations to players about the acceptable grounds for an exemption. That included the interpretation that having had a coronavirus infection within the previous six months would qualify.

The federal government disagreed.

The Victoria state government mandated that all players, staff, fans and officials must be fully vaccinated for COVID-19 to enter the tournament.

The state, which approved the medical exemptions for Djokovic, said those exemptions for were for access to Melbourne Park, not the border.

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

Tournament director Craig Tiley has continued working in the background with Djokovic.

Tiley’s video message to Australian Open staff about the tournament’s “difficult time in the public arena” was published in News Corp. newspapers Saturday.

“There’s been a circumstance that relates to a couple of players, Novak particularly . . . in a situation that is very difficult,” Tiley said in the video. “We’re a player-first event. We’re working closely with Novak and his team, and others and their team, that are in this situation.”

The 34-year-old Djokovic was one of two players put into detention in a hotel in Melbourne that also houses refugees and asylum seekers. A third person, reported to be an official, left the country voluntarily after border force investigations.

The other player was 38-year-old doubles player Renata Voráčová, who had already been in Australia for a week before an investigation by the border officials. She told media from the Czech Republic she’d been confined to a room and there was a guard in the corridor.

Djokovic reached out to the world for the first time in three days on Friday night, posting on social media to mark the Orthodox Christmas and thank his supporters. There’s been large-scale rallies in Belgrade and small groups of supporters have gathered daily outside his detention hotel.

“Thank you to the people around the world for your continuous support,” Djokovic posted on Instagram. “I can feel it and it is greatly appreciated.”

Djokovic, after months of speculation he’d miss the tournament because of his stance on vaccination, announced on Tuesday via social media that he’d received a medical exemption to play in the tournament.

Prime Minister Morrison said that may have raised the attention of border officials.

Tiley said in his video to Australian Open staff that he couldn’t speak publicly because of the ongoing legal matter but defended his organization.

“There’s a lot of finger pointing going on and a lot of blaming going on,” he said in the video, “but I can assure you our team has done an unbelievable job and have done everything they possibly could according to all the instructions that they have been provided.”

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

In an emailed response to The Associated Press about what could transpire if Djokovic loses his legal fight, the Australian Border Force said: “A person whose visa has been canceled may be subject to a three-year exclusion period that prevents the grant of a further temporary visa.”

“The exclusion period will be considered as part of any new visa application and can be waived in certain circumstances, noting each case is assessed on its own merits.”