Naomi Osaka will be hoping to be fit for the Australian Open after the reigning champion withdrew from the Melbourne Summer Set 1.

Osaka, who won the most recent of her four grand slam titles last year at Melbourne Park, has looked in fine form this week in her first appearances since returning from the break she took from tennis last year.

The top seed beat Alize Cornet, Maryna Zanevska and Andrea Petkovic en route to the semi-finals, but could not compete against Veronika Kudermetova on Saturday, citing an abdominal injury.

Osaka explained that her body had taken a hit from playing such intense matches in consecutive days, and she instead is looking to rest and recover ahead of the first grand slam of the season, which starts on January 17.

"Sad to withdraw due to injury from my match today, my body got a shock from playing back to back intense matches after the break I took," Osaka tweeted.

"Thank you for all the love this past week [Red heart] I’ll try to rest up and I’ll see you soon!"

Osaka's injury has prevented what looked to be an enticing showdown with Simona Halep, who guaranteed a place in a WTA Tour singles final for a 13th successive season by beating Chinese teenager Zheng Qinwen 6-3 6-2.

Halep's first final came in 2010 and she has taken just a week to get back into her stride after an injury-ravaged 2021 season.

The Romanian, a two-time grand slam champion, went into the week ranked at world number 20, her lowest position at the start of a season since 2013.

However, she has now reached at least the semi-final stage in three successive tournaments, and she will fancy her chances against third seed Kudermetova, who is into her third singles final.

Novak Djokovic thanked the supporters campaigning for him to be allowed to play at the Australian Open as he spoke out for the first time since being detained in Melbourne.

The ATP world number one will spend the weekend in a hotel that also houses refugees and asylum seekers, some of whom have been waiting years for the chance of freedom.

A court hearing on Monday should determine Djokovic's fate after Border Force officials cancelled his visa application, stating the 34-year-old had "failed to provide appropriate evidence to meet the entry requirements to Australia".

Djokovic seemed all set to play after he was granted a medical exemption by organisers of the first grand slam of the year, but his fate now hangs in the balance. An injunction secured by his legal team has allowed him to remain in the country for now, albeit in detention.

The Serbian superstar wrote on Instagram: "Thank you to people around the world for your continuous support. I can feel it and it is greatly appreciated."

That came after a message from Djokovic to mark Orthodox Christmas on Friday, as he wrote: "Peace of God. Christ was born. Merry Christmas. May God's love strengthen and fulfil you."

The Australian Open begins on January 17 and this is just about the worst possible preparation for the 20-time major winner, even if he is given permission to remain in Australia at Monday's hearing.

There was an outcry from many Melburnians when Djokovic announced on Tuesday that he was on his way to the tournament with an exemption pass.

A small number have since protested that Djokovic should be liberated, while he has found some support on social media and extensive backing from his homeland, with Serbian president Aleksandar Vucic accusing Australian authorities of "harassment of the best tennis player in the world", pledging to "fight for Novak Djokovic, for justice and truth".

Djokovic is a record nine-time champion at Melbourne Park, but there is said to be a strong feeling locally that he should have to show proof of being vaccinated against COVID-19, given the efforts residents have gone to and the stringent restrictions imposed on them during the pandemic to date.

Australian Open officials have claimed "rigorous" checks were put in place to assess the veracity of any claim for an exemption.

One theory that has been widely suggested is Djokovic, who has spoken out about vaccine matters in the past, may have been awarded the exemption on the basis he had a positive test for COVID-19 in the past six months. He has not publicly confirmed he has recently had the virus.

However, reports from Australia have stated federal government officials instructed Tennis Australia in recent months that experiencing a recent case of coronavirus was not an adequate explanation for a player not being fully vaccinated.

Djokovic's wife, Jelena, issued a statement in support of her husband, posting on Instagram: "We wish we are all together today, but my consolation is that at least we are healthy. And we will grow from this experience.

"Thank you dear people, all around the world for using your voice to send love to my husband. I am taking a deep breath to calm down and find gratitude (and understanding) in this moment for all that is happening.

"The only law that we should all respect across every single border is love and respect for another human being. Love and forgiveness is never a mistake but a powerful force."

Australian authorities, all the way up to prime minister Scott Morrison, have contended their border laws are there for a good reason, with Monday promising to be a seismic day in the capital of Victoria.

Ash Barty set a new personal best for aces in a match as she rifled 17 past Sofia Kenin on the way through to the Adelaide International 1 semi-finals.

Reigning Wimbledon champion Barty won 31 of 32 points on first serve in a ruthless 6-3 6-4 victory over the 2020 Australian Open winner.

It sets up a tantalising last-four clash with Poland's defending champion Iga Swiatek, who is a frequent practice partner for Australian home favourite Barty.

Explaining her stunning serving performance, Barty said: "I think towards the end Sofia was kind of leaning one way or the other, and I was able to kind of get up and hit my spots."

Facing former French Open winner Swiatek will be a major early-season test for the world number one, with the Warsaw-born 20-year-old fending off former grand slam winner Victoria Azarenka 6-3 2-6 6-1 in Friday's quarter-final.

The other semi-final in Adelaide will see Misaki Doi take on Elena Rybakina after both won in three sets to get there, seeing off Kaja Juvan and Shelby Rogers respectively.

Melbourne Park is staging two tournaments this week, and there is the prospect of a starry final in Melbourne Summer Set 1, with Naomi Osaka and Simona Halep both through to the last four.

Top seed Osaka beat experienced German Andrea Petkovic 6-1 7-5, while second seed Halep had to scrap for a 6-2 5-7 6-4 win against Viktorija Golubic of Switzerland.

Osaka took inspiration from Petkovic's fight in the second set of their contest. Quoted on the tournament website, she said: "It was really cool how she didn't give up for any point, so I just felt like I should do the same thing and see what happens."

Halep said her encounter with Golubic had been "really difficult", adding: "I didn't really trust that I can win this match, but I fought to the end, and I'm very proud of this."

Saturday's semi-finals of Melbourne Summer Set 2 will seed Daria Kasatkina take on Amanda Anisimova, while Ann Li plays Aliaksandra Sasnovich.

Rafael Nadal was handed a walkover to the semi-finals of the Melbourne Summer Set tournament when his opponent withdrew with a foot injury.

In an ironic development, given Nadal has been so plagued by his own serious foot problems, Tallon Griekspoor had to pull out of his scheduled clash with the 20-time grand slam champion on Friday.

That was perhaps not the news Nadal wanted, given the Spaniard is competing this week to gain much-needed match practice ahead of the Australian Open. It is his first ATP Tour event since August, when a long-existing left foot problem caused him to curtail his season.

Withdrawing from a Rod Laver Arena tussle with Nadal was a painful blow to 25-year-old Dutchman Griekspoor too, and he wrote on Twitter: "These are the matches you play for."

It would have been a first career meeting with all-time great Nadal for the world number 65, who instead faces a fitness battle before the first grand slam of the year begins on January 17.

Nadal will go on to face Finland's Emil Ruusuvuori, who won 6-2 6-1 against Slovakian Alex Molcan. The other semi-final on Saturday will see Bulgarian third seed Grigor Dimitrov tackle American qualifier Maxime Cressy.

At the Adelaide International, the top three seeds sauntered through to the semi-finals. Top seed Gael Monfils brushed aside Tommy Paul 6-4 6-1, number two Karen Khachanov saw off Egor Gerasimov 7-5 6-3, and third seed Marin Cilic was a 6-3 6-2 winner over Laslo Djere.

It was also confirmed on Friday that former world number one Andy Murray has been awarded a wildcard into next week's Sydney Classic.

Murray suffered a first-round exit in Melbourne and is looking for a run of matches before launching his campaign at the Australian Open, where he is a five-time runner-up.

Roberto Bautista Agut saw Spain through to a second ATP Cup final by beating Hubert Hurkacz after Pablo Carreno Busta outclassed Jan Zielinski in Sydney on Friday.

Bautista Agut made it mission accomplished for Spain by defeating Poland's world number nine 7-6 (8-6) 2-6 7-6 (7-5) at the Ken Rosewall Arena.

Spain were beaten by Serbia in the final two years ago, but will get another opportunity to lift the trophy on Sunday when they face Canada or Russia.

Bautista Agut has won all four matches he has played in the competitions this week and came out on top despite Hurkacz hitting 61 winners to his 28.

The 33-year-old only made 14 unforced errors and secured the only mini-break in a final-set tie-break to put Spain into the final once again.

He said: "It's a match that I will always remember. I think both of us could get the win today. He also really deserved a lot of good things. But this is our game, this is tennis.

"Today I was the one who got the win. I think I also deserved it. I did a lot of good things on the court."

Novak Djokovic has been warned by Boris Becker that his "stubbornness" could prevent him being remembered as the greatest tennis player that ever lived.

World number one Djokovic, who has not declared his COVID-19 vaccination status, seemed set to play in this month's Australian Open after he was granted a medical exemption by tournament organisers.

That was required for any player who has not been fully vaccinated. One theory that has been widely suggested is that Djokovic may have been entitled to an exemption after a positive test for COVID-19 in the past six months, although he has not confirmed he has recently had the virus.

However, Djokovic is now set to spend the weekend in a Melbourne detention hotel in which refugees and asylum seekers are also being kept, after Australian Border Force's decision to cancel his visa application.

A court hearing on Monday should provide a resolution to the saga, with Djokovic's legal team set to battle for his right to enter the country and play in the season's first grand slam, at which he would be bidding to win a record 21st men's singles major title. The Australian Open gets under way on January 17.

Becker coached Djokovic for three seasons, from 2014 to 2016, and told the Daily Mail the 34-year-old Serbian is "making a big mistake in not getting vaccinated".

The German said the decision "is one that threatens what remains of his career and his chance to cement himself as the greatest player of all time".

Becker, a six-time grand slam winner, said: "The same incredible determination which I saw win so many close matches can be a vulnerability with his stubbornness.

"It is not just about Australia. The fact is that we are living in a different world and he is going to find it very hard to live the life of a professional tennis player travelling around without the vaccination.

"Maybe one day we will get back to a more normal situation, but at 34 he does not have much time left to pursue his goals."

There have been protests on the streets of Melbourne and Belgrade, with arrests made by police in the Victorian capital, while Djokovic found some support from within the tennis fraternity on Friday, as American John Isner backed his case.

Isner wrote on Twitter: "What Novak is going through right now is not right. There’s no justification for the treatment he’s receiving. He followed the rules, was allowed to enter Australia, and now he’s being detained against his own will. This is such a shame. #IStandWithNovak".

Nick Kyrgios, who has had his run-ins with Djokovic in the past, labelled Australia's handling of the situation "really bad", while former world number one Andy Roddick also appears to be in Djokovic's corner.

Yet Australia's home affairs minister Karen Andrews rejected any idea that Djokovic was being "held captive".

Andrews told the ABC: "Can I say, firstly, that Mr Djokovic is not being held captive in Australia. He is free to leave at any time that he chooses to do so and Border Force will actually facilitate that.

"Yes, there was a visa issued – that is actually not the issue. It is the second part of that process, which is the specific entry requirements to be able to cross Australia's border and to enter Australia lawfully."

She said Djokovic was not the only tennis case that was under investigation by Australian authorities. A player and an official are reported to be under scrutiny.

"I'm aware of investigations in relation to two individuals by the Australian Border Force," Andrews said. "They're going through their processes of investigation.

"And at some time, they will brief me, but all I can absolutely assure you and the rest of Australia of is that the Australian Border Force will take absolutely the appropriate action."

The Professional Tennis Players Association (PTPA) has issued an update on Novak Djokovic, expressing their view that he should be allowed to compete at the Australian Open with an approved medical exemption.

World number one Djokovic, who has not declared his COVID-19 vaccination status, seemed set to play in the year's opening major, which he has won nine times previously, after he confirmed he had received a medical exemption to compete.

Protocols in Australia require proof that players have been vaccinated or have a medical exemption to compete at Melbourne Park.

Tournament director Craig Tiley insisted that the 20-time major champion had not been given a "special favour" to play in the tournament, though the decision faced immediate and widespread backlash and on Wednesday, Djokovic's visa application was cancelled.

However, the Serbian's legal team filed for a judicial review, with the case to be heard by Federal Circuit Court Judge Anthony Kelly on Monday at 10am local time in Melbourne.

Djokovic is now hauled up in a Melbourne hotel, and cannot be deported until the hearing has taken place unless he leaves the country of his own volition.

Protestors have also appeared outside of the hotel where Djokovic has been transferred, while Nick Kyrgios has expressed his displeasure at the way the situation has been handled.

The matter has also drawn criticism from Serbia's president Aleksandar Vucic, who labelled Australia's treatment of the nation's superstar as "harassment."

On Friday, the PTPA - which was founded by Djokovic and Canadian player Vasek Pospisil in 2020 - issued an update on the situation.

The PTPA has been diligently monitoring the detainment of professional tennis player Novak Djokovic by the Australian Government.

"The PTPA has been in close contact with Mr Djokovic, his family and legal counsel, government officials and Australian Open leadership," a statement read.

"Mr Djokovic has verified his well-being to us. He has also requested that we allow him to personally share the facts of his detainment in his own words, and in his own time.

"With the utmost respect for all personal views on vaccinations, vaccinated athletes and unvaccinated athletes (with an approved medical exemption) should both be afforded the freedom to compete. We will continue to support and advocate for our members, and all players, in a manner that is acceptable to them."

The statement concluded with: "We will continue to monitor his health, safety and well-being. We look forward to his time back on the court."

Nick Kyrgios has labelled the reaction to and handling of Novak Djokovic's predicament as "really bad".

Djokovic faces deportation from Australia after having had his visa application cancelled.

The world number one has not revealed his vaccination status against COVID-19, but was set to compete at the Australian Open under a medical exemption.

That decision called uproar in Australia, which has been under strict lockdown restrictions for much of the pandemic.

However, Djokovic was denied entry into Australia upon his arrival at Melbourne airport, with Australian Prime Minister Scott Morrison saying the 20-time grand slam champion would be on "the next plane home" if he failed to produce a sufficient reason for his medical exemption.

Australian Open tournament director Craig Tiley insisted that the 20-time major champion had not been given a "special favour" to play in the tournament, though the decision faced immediate and widespread backlash.

Djokovic is currently hauled up in a hotel after an interim injunction hearing was pushed back to Monday at 10am local time, with Federal Circuit Court Judge Anthony Kelly ruling that the Serbian could not be deported until at least 4pm on Monday, local time.

Several of Djokovic's fellow players, including Rafael Nadal, have criticised the 34-year-old's stance and the decision to initially allow him to compete.

Yet Kyrgios, who has never seen eye to eye with Djokovic, has not joined those critics, and instead hit out at how Australia, and the media, have handled the situation.

"Look I definitely believe in taking action, I got vaccinated because of others and for my mum's health, but how we are handling Novak’s situation is bad, really bad," Kyrgios tweeted on Friday.

"Like these memes, headlines, this is one of our great champions but at the end of the day, he is human. Do better."

Kyrgios said in November that he believed the Australian Open should be cancelled if it was mandated that competitors would have to be vaccinated.

 "I don't think the Aus Open should go ahead, just for the people in Melbourne – you’ve got to send a message," Kyrgios said on his 'No Boundaries' podcast at the time.

Felix Auger-Aliassime pulled off a terrific win over Alexander Zverev to carry Canada through to the ATP Cup semi-finals.

After Great Britain beat the United States 2-1 earlier to stake a claim for a last-four spot, Canada's singles players rose to the challenge to see off Germany.

That meant disappointment for Dan Evans and the British team, with Canada progressing to a clash with Russia as winners of Group C.

Denis Shapovalov got the better of Jan-Lennard Struff in a tight tussle, the world number 14 beating 51st-ranked Struff 7-6 (7-5) 4-6 6-3, giving Auger-Aliassime a swing at Olympic Games and ATP Finals champion Zverev before a possible doubles decider.

The world number 11 duly got the better of third-ranked Zverev by a similar score to the opening singles rubber, winning 75 per cent of first-serve points as he came through 6-4 4-6 6-3 late at night in Sydney.

Great Britain had impressed in edging out the US team, with Dan Evans beating John Isner and then teaming up with Jamie Murray to see off Isner and Taylor Fritz 6-7 (3-7) 7-5 10-8 in a dramatic doubles decider. Fritz beat Cameron Norrie in the second singles rubber.

Daniil Medvedev played a pivotal role as Russia wrapped up a perfect 3-0 match record in Group B, beating Italy 2-1 to nail down their semi-final place.

Defending champions Russia, who also won the Davis Cup last year, were on the back foot early on against Italy after Jannik Sinner beat Roman Safiullin, but US Open champion Medvedev ground out a 6-2 6-7 (5-7) 6-4 win over Matteo Berrettini to take the match – and the battle for top spot in the group – down to a doubles decider.

Medvedev and Safiullin were given a stiff test by their singles foes on the doubles court but had just enough to beat Berrettini and Sinner 7-5 4-6 10-5.

Rafael Nadal declared his first singles match on the ATP Tour for five months a roaring success after the Spaniard battled past Ricardas Berankis in Melbourne.

A 6-2 7-5 win for Nadal over the Lithuanian qualifier carried the 35-year-old into the quarter-finals of the Melbourne Summer Set tournament.

Playing on Rod Laver Arena, the main show court for the upcoming Australian Open, top seed Nadal was tested by Berankis but came through unscathed, breaking serve to love to clinch the victory.

This was the first time that Nadal had faced Berankis, the world number 104 who briefly entered the top 50 five years ago, and it came as the 20-time grand slam winner battles back from the left foot injury that curtailed his 2021 season.

Nadal had not competed on tour since losing to Lloyd Harris in the third round in Washington in August, and the match practice he gained at an exhibition event in Abu Dhabi last month was followed by him contracting COVID-19.

He is vaccinated though, so was able to travel once he recovered from that brush with coronavirus, and is looking to build up form and fitness before the Australian Open begins.

"Honestly, I've been going through some difficult, challenging moments the last year and a half, but in general terms I'm super happy to be back in competition," Nadal said.

"It's important to start with a victory. It gives me the chance to play another time tomorrow and that's the main thing at this moment because I didn't play for such a long time.

"The main thing is being healthy. That's probably the only thing."

Awaiting Nadal in the last-eight stage will be Dutch player Tallon Griekspoor, who fended off Australia's Alexei Popyrin in three sets.

Determined not to take on too heavy a workload, Nadal has pulled out of the doubles tournament, despite making a winning start on Tuesday when he paired up with fellow Spaniard Jaume Munar.

He elected to play doubles initially to build up some rhythm. "In doubles, things always happen fast," Nadal said. "It makes you feel alive on the tour again. I think that was a positive thing."

Third seed Grigor Dimitrov advanced, seeing off Andy Murray's conqueror Facundo Bagnis in three sets, but Belgian fourth seed David Goffin slumped to a 7-5 6-3 loss against Slovakian Alex Molcan.

At the Adelaide International 1 tournament, there were wins at the last-16 stage for the top three seeds – Gael Monfils, Karen Khachanov and Marin Cilic – but fourth seed Frances Tiafoe was caught out by Australian Thanasi Kokkinakis, losing in three sets.

Novak Djokovic will remain in Australia until at least Monday, when a hearing on his appeal against deportation will take place.

World number one Djokovic, who has not declared his COVID-19 vaccination status, seemed set to play in this month's Australian Open after he was granted a medical exemption.

Protocols in Australia require proof that competitors and staff have been jabbed or have a medical exemption to compete at Melbourne Park.

Tournament director Craig Tiley insisted that the 20-time major champion had not been given a "special favour" to play in the tournament, though the decision faced immediate and widespread backlash.

On Wednesday, Djokovic faced deportation after Australian Border Force's decision to cancel his visa application, with Prime Minister Scott Morrison declaring "rules are rules."

However, the Serbian's legal team have filed for a judicial review, with the case to be heard by Federal Circuit Court Judge Anthony Kelly on Monday at 10am local time in Melbourne.

Due to a delay in receiving the application for a review of the visa decision and the temporary ban on Djokovic's deportation, it has been agreed that the 34-year-old should remain in Australia until at least Monday. 

Djokovic can leave Australia of his own volition. 

Protestors have also appeared outside of the hotel where Djokovic has been transferred, supporting the nine-time Australian Open winner.

The matter has also drawn criticism from Serbia's president Aleksandar Vucic, who labelled Australia's treatment of the nation's superstar as "harassment." 

Rafael Nadal, meanwhile, suggested Djokovic had made life difficult for himself by refusing to reveal his vaccination status.

"The only thing that I can say is I believe in what the people who know about medicine says, and if the people say that we need to get vaccinated, we need to get the vaccine," Nadal said.

"I went through COVID. I have been vaccinated twice. If you do this, you don't have any problem to play here. The world in my opinion has been suffering enough to not follow the rules.

"I think if he wanted, he would be playing here in Australia without a problem. He made his own decisions, and everybody is free to take their own decisions, but then there are some consequences."

The Australian Open starts on January 17.

Rafael Nadal declared it was imperative to "follow the rules" on COVID-19 vaccinations after rival Novak Djokovic was told he faces being deported from Australia.

World number one Djokovic was left fighting for the right to compete at the Australian Open, a tournament he has won nine times, after authorities cancelled his visa.

A medical exemption was expected to allow Djokovic to enter the country, regardless of his vaccination status, which he has yet to formally disclose.

However, the Australian Border Force declared the Serbian had been ordered to fly out of the country on Thursday, sparking a challenge to that decision by Djokovic's legal team.

Reports in Australia said an interim injunction had been granted, meaning Djokovic will remain in immigration detention until a court hearing on Monday.

According to Nadal, who had COVID-19 recently but has been cleared to compete at Melbourne Park, Djokovic would have made his life a lot easier by going down the vaccination route.

"It's normal that the people here in Australia get very frustrated with the case because they have been going through a lot of very hard lockdowns, and a lot of people were not able to come back home," Nadal said.

"The only thing that I can say is I believe in what the people who know about medicine says, and if the people say that we need to get vaccinated, we need to get the vaccine.

"I went through COVID. I have been vaccinated twice. If you do this, you don't have any problem to play here. The world in my opinion has been suffering enough to not follow the rules.

"I think if he wanted, he would be playing here in Australia without a problem. He made his own decisions, and everybody is free to take their own decisions, but then there are some consequences."

Djokovic was initially detained at an airport after arriving in Australia, while his status remained in limbo. His coach, Goran Ivanisevic, said it had been "not the most usual trip Down Under".

Spanish superstar Nadal has 20 grand slam titles, the same number that Djokovic and Roger Federer have brought up across their careers. They are locked in a race to finish with the most majors, and Federer, at 40, is battling back from injury and unlikely to compete at a slam before the US Open.

Australia's Prime Minister Scott Morrison tweeted on Thursday: "Mr Djokovic's visa has been cancelled. Rules are rules, especially when it comes to our borders.

"No one is above these rules. Our strong border policies have been critical to Australia having one of the lowest death rates in the world from COVID, we are continuing to be vigilant."

Nadal has some sympathy for Djokovic, but it appears to be limited.

"Of course, I don't like the situation that is happening," Nadal said. "In some way I feel sorry for him. But at the same time, he knew the conditions since a lot of months ago, so he makes his own decision."

Novak Djokovic was left fighting for the right to compete at the Australian Open on Wednesday after authorities cancelled his visa.

The world number one announced on Tuesday that he had received a medical exemption to play in the tournament he has won a record nine times. 

That medical exemption was expected to allow Djokovic to enter the country, regardless of his vaccination status, which he has yet to formally disclose.

However, the Victorian government reportedly rejected an application as a member of Djokovic's support team made an error in requesting a sub-class of visa.

Further doubt was cast over Djokovic's chances of being allowed to contest the first grand slam of the year when Jaala Pulford, the acting sports minister of the state of Victoria, later declared on social media that the Serbian's application will not be supported.

It was later announced by the Australian Border Force (ABF) he had been ordered to fly out of the country on Thursday, although his legal team was said to be challenging the decision.

"The ABF can confirm that Mr Djokovic failed to provide appropriate evidence to meet the entry requirements to Australia, and his visa has been subsequently cancelled," the force said.

"Non-citizens who do not hold a valid visa on entry or who have had their visa cancelled will be detained and removed from Australia.

"The ABF can confirm Mr Djokovic had access to his phone.​"

Djokovic's father had earlier accused authorities of holding the 20-time major winner "captive for five hours".

He told Russian news agency Sputnik: "This is a fight for the libertarian world, not just a fight for Novak, but a fight for the whole world.

"If they don't let him go in half an hour, we will gather on the street. This is a fight for everyone."

Novak Djokovic is "being held captive" in a room guarded by police after arriving in Melbourne for the upcoming Australian Open, the tennis star's father has alleged.

World number one Djokovic announced on Tuesday that he had received a medical exemption to play in the tournament he has won a record nine times. 

That medical exemption was expected to allow Djokovic to enter the country, regardless of his vaccination status, which he has yet to formally disclose.

However, the Victorian government reportedly rejected an application from Border Force as a member of Djokovic's support team made an error in requesting a sub-class of visa.

Further doubt was cast over Djokovic's chances of being allowed to contest the first grand slam of the year when Jaala Pulford, the acting sports minister of the state of Victoria, later declared on social media that the Serbian's application will not be supported.

And amid later reports that the 20-time major winner could be forced to fly back home, Djokovic's father Srdjan hit out at authorities for their treatment of his son. 

"Novak is currently in a room which no one can enter," he told the B92 internet portal. "In front of the room are two policemen."

Srdjan added to Russian news agency Sputnik: "I have no idea what's going on. My son has been held captive for five hours.

"This is a fight for the libertarian world, not just a fight for Novak, but a fight for the whole world.

"If they don't let him go in half an hour, we will gather on the street, this is a fight for everyone."

The latest twist in the Djokovic saga comes after Australian prime minister Scott Morrison stated that Djokovic "will be on the next plane home" if he fails to prove he merits medical exemption to play in the tournament.

Australian Open director Craig Tiley insisted on Tuesday that Djokovic had not been given a "special favour" to play in the tournament, which is scheduled to run from January 17 until January 30.

Novak Djokovic's participation at the Australian Open is reportedly back in doubt due to an issue with his visa.

World number one Djokovic flew into Melbourne on Wednesday, a day after revealing he had been cleared to take part in the tournament after receiving a medical exemption.

The Serbian has not directly addressed whether he has been vaccinated against COVID-19, but players who compete at Melbourne Park either require proof they have been jabbed or an exemption.

He has spoken openly and critically about vaccine mandates, insisting there should be freedom of choice in all walks of life.

Many Australians criticised the decision to welcome Djokovic into the country, but the 34-year-old appears to have hit another stumbling block in his battle to defend the title he has won a record nine times.

Reports from Australia suggested that the Victorian government had rejected an application from Border Force regarding Djokovic's visa as a member of his support team made an error in requesting a sub-class of visa.

And Jaala Pulford, the acting sports minister of the state of Victoria, later declared on social media that Djokovic's application will not be supported.

"The Federal Government has asked if we will support Novak Djokovic's visa application to enter Australia," she posted on Twitter.

"We will not be providing Novak Djokovic with individual visa application support to participate in the 2022 Australian Open Grand Slam.

"We've always been clear on two points: visa approvals are a matter for the Federal Government, and medical exemptions are a matter for doctors."

The latest twist in the Djokovic saga comes after Australian prime minister Scott Morrison stated that Djokovic "will be on the next plane home" if he fails to prove he merits medical exemption to play in the tournament.

Australian Open director Craig Tiley insisted on Tuesday that the 20-time major champion had not been given a "special favour" to play in the tournament, which is scheduled to run from January 17 until January 30.