World number one Novak Djokovic has withdrawn from the ATP Cup in Sydney amid ongoing uncertainty over his title defence at next month's Australian Open.

Djokovic has not yet confirmed his place at January's Grand Slam due to the COVID-19 mandate in Victoria.

The 34-year-old's father, Srdjan, has previously said that the nine-time Australian Open champion is unlikely to feature in Melbourne unless vaccination rules are relaxed.

World number 33 Dusan Lajovic will now lead the Serbia team at the ATP Cup.

Meanwhile, Austria have been replaced by France at the event following the withdrawals of Dominic Thiem and Dennis Novak. The French will be led by world number 35 Ugo Humbert, alongside Arthur Rinderknech, Edouard Roger-Vasselin and Fabrice Martin.

Russia's Andrey Rublev, Aslan Karatsev and Evgeny Donskoy have withdrawn, with Evgeny Karlovskiy joining the team, while Team USA's Austin Krajicek has also pulled out.

The ATP Cup will begin on New Year's Day at both Ken Rosewall Arena and Qudos Bank Arena, Sydney Olympic Park.

Dominic Thiem has withdrawn from next month's Australian Open.

Thiem has not played on the ATP Tour since suffering a wrist injury at the Mallorca Championships in June.

The 2020 US Open champion was due to feature in the Mubadala World Tennis Championship in Abu Dhabi this month, but withdrew after suffering a setback.

Thiem on Tuesday revealed his wrist is in "optimal condition", but the Austrian will miss the first grand slam of the year at Melbourne Park and will instead make his comeback at the Cordoba Open next month.

The Austrian tweeted: "As you all know, I came back home to Austria to recover after hard practice sessions I had in Dubai and the slight setback in my preparation. I am now feeling well again, my wrist is in optimal condition and I am practicing normally with a very good intensity.

"After my short holidays, my team and I have assessed all matters and we have decided to make some changes to my initial tournament schedule.

"I will start the season in South America at the Cordoba Open in Argentina, end of January, and therefore I will not play this year at the Australian Open in Melbourne, a city that I love and where I have great memories of unforgettable matches in front of amazing crowds. I will miss the Australian fans but I will be back in 2023.

"We believe this is the right decision in order to have a good return to competition. For the moment I will remain in Austria for a few more days and then head to practice outdoors and get ready for my first event of the season."

The 28-year-old was a runner-up in the 2020 Australian Open before going on to claim his first major title at Flushing Meadows.

Alexander Zverev believes he will form a big three with Novak Djokovic and Daniil Medvedev in 2022 but hopes he will not get the chance to become world number one at the Australian Open.

The German is knocking on the door near the top of the rankings after a fine year that saw him win six titles, including the season-ending ATP Finals in Turin and an Olympic gold medal in Tokyo.

Zverev, currently ranked third, could go top of the rankings if he wins the Australian Open, which starts next month, but that is only possible if current world number one Djokovic does not play.

And Zverev is hopeful the Serbian will take part despite continued uncertainty over his participation in the tournament amid intense debate over his COVID-19 vaccine stance.

Djokovic, a nine-time Australian Open winner, is yet to disclose his vaccination status.

Tournament chief Craig Tiley said this week he is still hoping to see the tour's top player participate if he meets the required conditions, which are either being vaccinated or having a medical exemption.

"The situation with Novak and Australia is still a big question mark," Zverev said in a podcast appearance with Eurosport Germany. 

"Of course, I hope that he will be allowed to play, that is very clear.

"There are thousands of mathematical calculations, if he doesn't play Australia and I win the Australian Open, then I'm number one in the world and so on and so forth.

"At the end of the day, now is not the time to think about [being world number one]. Now is the time to prepare as best as you can so you're physically able to play for it."

As well as his silverware, Zverev made the last four of the French Open and US Open, and the 24-year-old believes his experience has begun to come to the fore.

Zverev had a 59-15 record this season and recorded at least one victory against every other player inside the top 10 of the ATP year-end rankings.

"I've become much calmer and I'm also getting older," he added.

"I'm not 18 or 19 anymore. I understand maybe a bit more things about life and understand that you just have to keep calm in important situations. That has had its effect on me this year.

"I think next year could be very similar to the last six months from this year.

"Before, there used to be always talk about Rafael Nadal, Roger Federer and Novak Djokovic – now the big titles were the Olympics, US Open, Turin and Wimbledon, and they were all won by Medvedev, Djokovic and me. 

"I don't expect it to be any different next year."

Alexander Zverev believes he will form a big three with Novak Djokovic and Daniil Medvedev in 2022 but hopes he will not get the chance to become world number one at the Australian Open.

The German is knocking on the door near the top of the rankings after a fine year that saw him win six titles, including the season-ending ATP Finals in Turin and an Olympic gold medal in Tokyo.

Zverev, currently ranked third, could go top of the rankings if he wins the Australian Open, which starts next month, but that is only possible if current world number one Djokovic does not play.

And Zverev is hopeful the Serbian will take part despite continued uncertainty over his participation in the tournament amid intense debate over his COVID-19 vaccine stance.

Djokovic, a nine-time Australian Open winner, is yet to disclose his vaccination status.

Tournament chief Craig Tiley said this week he is still hoping to see the tour's top player participate if he meets the required conditions, which are either being vaccinated or having a medical exemption.

"The situation with Novak and Australia is still a big question mark," Zverev said in a podcast appearance with Eurosport Germany. 

"Of course, I hope that he will be allowed to play, that is very clear.

"There are thousands of mathematical calculations, if he doesn't play Australia and I win the Australian Open, then I'm number one in the world and so on and so forth.

"At the end of the day, now is not the time to think about [being world number one]. Now is the time to prepare as best as you can so you're physically able to play for it."

As well as his silverware, Zverev made the last four of the French Open and US Open, and the 24-year-old believes his experience has begun to come to the fore.

Zverev had a 59-15 record this season and recorded at least one victory against every other player inside the top 10 of the ATP year-end rankings.

"I've become much calmer and I'm also getting older," he added.

"I'm not 18 or 19 anymore. I understand maybe a bit more things about life and understand that you just have to keep calm in important situations. That has had its effect on me this year.

"I think next year could be very similar to the last six months from this year.

"Before, there used to be always talk about Rafael Nadal, Roger Federer and Novak Djokovic – now the big titles were the Olympics, US Open, Turin and Wimbledon, and they were all won by Medvedev, Djokovic and me. 

"I don't expect it to be any different next year."

Andy Murray will compete at the Australian Open for the first time in three years after being awarded a main-draw wildcard.

Murray has finished as a runner-up five times at Melbourne Park – most recently in 2016 when he was beaten by Novak Djokovic 6-1 7-5 7-6 (7-3).

The Scot has since struggled with a hip injury that had him on the verge of retirement, while he dropped to 134th in the world rankings.

However, the former world number one was in action at the Mubadala World Tennis Championship in Abu Dhabi last week, where he defeated Rafael Nadal before eventually falling to Andrey Rublev in the final of the exhibition event.

Murray was due to feature at the Australian Open in 2020 before a positive coronavirus test stopped him from playing, but the 34-year-old is thankful for the chance to compete in Melbourne again.

"I'm really excited to be back playing at the Australian Open and grateful to Craig [Tiley] and the team for the opportunity," Murray said on his wildcard, as quoted by the tournament's website.

"I've had some great times in Australia playing in front of the amazing crowds and I can't wait to step back out on court at Melbourne Park."

Tournament director and Tennis Australia chief executive Craig Tiley added: "Andy is renowned for his fighting spirit, passion and love of the game, and I'm delighted to welcome him back to Melbourne in January."

American Stefan Kozlov and Frenchman Lucas Pouille join Murray as the men's singles wildcards so far, with the other four spots likely to go to Australians and another to an Asia-Pacific player.

The Australian Open gets underway on January 17 with the final set to take place 13 days later.

Australian Open chief Craig Tiley wants Novak Djokovic to participate in Melbourne but will not ask the world number one to disclose any medical reason he has for being unvaccinated against COVID-19.

The first grand slam of 2022 begins on January 17, but it is unclear if reigning champion Djokovic will be competing.

The Serbian, a nine-time Australian Open winner, is yet to disclose his vaccination status.

Following guidance from the Victoria state government, all players, staff and spectators at Melbourne Park must have been fully vaccinated against coronavirus or hold a medical exemption.

Djokovic has been named on the list for the draw and is also due to represent Serbia at the ATP Cup in Sydney, which runs from January 1 to 9.

"If Novak shows up, he'll be vaccinated or have a medical exemption," Australian Open chief executive Tiley told the Australian Associated Press.

"If any player, fan [or] workforce is on site here, you're either vaccinated or you have a medical exemption that's approved and you're on the Australian Immunisation Register.

"That provides us with safety and an extra level of comfort on site.

"We want to have the best players here; I'd love to have Novak here. If he meets those conditions then great, if not, it's disappointing."

Tiley added he does not expect Djokovic to reveal any medical reason for which he may not have received the vaccine, should he receive a medical exemption to feature in the tournament.

"Medically, he doesn't talk to anyone about it. I'm not going to ask Novak that, it's none of my business," Tiley continued.

"[It's] his choice on his medical condition, it's his choice to keep personal and private like all of us would do with any condition we may or may not have. We are not going to force him or ask him to disclose that.

"[If he is here] I will know that he fulfils one of those conditions."

Rafael Nadal is set to play in Melbourne, though that is in doubt after the Spaniard tested positive for COVID-19 this week, following his appearance at the Mubadala World Tennis Championship in Dubai.

Tiley, however, believes Nadal will have recovered in time.

"I'm confident Rafa will be here," said Tiley. "Players that are testing positive now will complete a period of time until they are no longer infectious and they will be fine.

"If you are going to test positive and you want to play the Australian Open, your timing would be now."

Tokyo Olympics gold medalist Belinda Bencic has tested positive for COVID-19 ahead of next month's Australian Open and is experiencing "severe" symptoms.

World number 23 Bencic returned a positive test, along with Ons Jabeur, after competing at the Mubadala World Tennis Championship in Abu Dhabi.

The pair are the third and fourth players to have tested positive after travelling to the Abu Dhabi event, following 2021 US Open winner Emma Raducanu and 20-time major winner Rafael Nadal.

Bencic wrote on Twitter: "Unfortunately and even though I am fully vaccinated, I recently tested positive for Covid-19.

"I am currently isolating and taking all precautionary [measures] to get through this as best as possible as I am experiencing quite severe symptoms (fever, aches, chills)."

The Mubadala World Tennis Championship typically serves as a warm-up event prior to the Australian Open which is due to begin on January 17 in Melbourne.

World number 10 Jabeur, who defeated Bencic in Abu Dhabi, is experiencing "strong symptoms" and isolating in her native Tunisia.

Rafael Nadal has tested positive for coronavirus on his return to Spain, leaving his participation at the Australian Open in doubt.

The 20-time major champion played at the Mubadala Tennis Championship in Abu Dhabi last weekend and declared his mission a success despite consecutive defeats on his return from a foot injury.

Indeed, Nadal had only competed in two matches since losing to Novak Djokovic in the French Open semi-finals in June before testing his long-term foot problem against Andy Murray and most recently Denis Shapovalov.

However, the 35-year-old's plans to feature in the Melbourne ATP 250 ahead of the Australian Open in early January have suffered a setback after he tested positive for COVID-19 upon landing in his home country on Monday.

Nadal revealed the news on Twitter as he posted: "I wanted to announce that on my return home after playing the Abu Dhabi tournament, I have tested positive for COVID in the PCR test that was performed on me when I arrived in Spain.

"Both in Kuwait and Abu Dhabi we passed controls every two days and all were negative, the last being on Friday and having the results on Saturday.

"I am having some unpleasant moments but I hope that I will improve little by little. I am now homebound and have reported the result to those who have been in contact with me.

"As a consequence of the situation, I have to have total flexibility with my calendar and I will analyse my options. I will keep you informed of any decisions about my future tournaments!"

Nadal was eyeing the Australian Open, which starts on January 17, as his first major comeback, though he earlier admitted his entry was not guaranteed as he evaluated his foot injury and physical fitness.

"I cannot guarantee Australia one hundred per cent, because I need to go home and see how the body responds after these days," Nadal told reporters on Saturday. 

"I have time to make a decision. At this point in my career, I need to go day by day, study each movement well.

"I have been able to show a competitive level against good players even without being in perfect condition. There are things to improve but looking at things with perspective it has been a positive tournament [in Abu Dhabi].

"The main objective is to be healthy enough to do the things that I need to do and aspire to the objectives that I have always had. The illusion and passion continue to exist."

The ATP Tour event in Melbourne, which would be Nadal's first such tournament since August, is due to start on January 3.

Dominic Thiem will skip the Australian Open if he is not happy with his fitness at the end of December, the former US Open champion said on Sunday.

The 28-year-old has not played on the ATP Tour since suffering a wrist injury at the grass-court Mallorca Championships in June.

Thiem missed Wimbledon and could not defend his grand slam title at Flushing Meadows, with injury fears lingering ahead of the new season.

Despite not requiring surgery on the damaged wrist, Thiem has been unable to play competitively and experienced a fresh setback this month when he pulled out of the Mubadala World Tennis Championship, an exhibition event in Abu Dhabi.

In announcing that decision on December 14, Thiem said he was "not yet ready to compete at the highest level", and there was little to inspire confidence when he issued an update confirming he would not travel to play in two events ahead of the Australian Open.

Although Thiem still wants to play at Melbourne Park, where the slam begins on January 17, his prospects are hinging on him feeling significantly more optimistic about his game and fitness in a matter of days.

Thiem wrote: "After speaking to my team, we have decided to return to Austria, instead of flying directly to Australia.

"Unfortunately, I caught a cold [and tested negative for COVID-19] while in Dubai and was unable to practise last week. I will therefore not be in the physical condition required to be able to play the ATP Cup and Sydney ATP 250.

"After not competing for the last six months I can't take the risk of coming back too soon and picking up a further injury.

"Overall, the time I spent in Dubai was great as I've increased the intensity and level of practise and my wrist is almost at 100 per cent.

"My aim is still to play the Australian Open but we will make a final decision about my participation by the end of December."

Dominic Thiem's comeback has been further delayed as the 2020 US Open champion does not feel ready to return at this week's Mubadala World Tennis Championship.

Austrian star Thiem has been out of action since suffering a wrist injury at the Mallorca Championships in June.

The 28-year-old missed Wimbledon and was unable to defend his title at Flushing Meadows, but he appeared to be on course to make his comeback before the end of 2021 after revealing in October he does not require surgery on his wrist.

However, the world number 15 is now facing a battle to be back to full fitness for January's Australian Open after withdrawing from an exhibition event in Abu Dhabi.

"I was looking forward to making my return to competition at Abu Dhabi but I feel that I am not yet ready to compete at the highest level," the 17-time ATP Tour champion posted via Twitter on Tuesday.

"It's disappointing to not take part this year but I need to continue my preparation for the upcoming season."

Thiem follows Casper Ruud in pulling out of the tournament, which begins on Thursday, while Emma Raducanu is out of the women's singles after testing positive for coronavirus.

Dan Evans and Taylor Fritz have taken the places of former world number three Thiem and Ruud, joining Andrey Rublev, Denis Shapovalov, Andy Murray and defending champion Rafael Nadal in the draw.

Andy Murray has parted ways with his long-term coach Jamie Delgado ahead of the 2022 season.

Murray and Delgado joined forces during the 2016 season when the Scot won a second Wimbledon title and finished the year top of the world rankings.

Former professional player Delgado, 44, then stepped up as full-time coach when Ivan Lendl stopped working in the role the following year, though much of his time has been spent with Murray negotiating a hip injury.

Delgado will now move on to go work with Denis Shapovalov's team, while Murray will continue to trial with Jan de Witt at an exhibition event in Abu Dhabi.

The 34-year-old had previously been working Johanna Konta's former coach Esteban Carril at a Stockholm tournament in November, but the Spaniard will not be part of Murray's setup for the upcoming season.

Potential new coach De Witt counts Gilles Simon, Gaels Monfils and Viktor Troicki as former players he has worked with, and the German will be with Murray for his first match against Dominic Thiem at the Mubadala World Tennis Championship.

Murray, who has dropped to 134th in the world rankings, will face Rafael Nadal if he can beat the Frenchman, while Emma Raducanu will also be in action in Abu Dhabi.

Rafael Nadal is set to start his 2022 season at the Melbourne ATP 250 ahead of the Australian Open.

Nadal this week appeared on the entry list for the first grand slam of the year, which begins on January 17.

The Spaniard has not featured on the ATP Tour since August, when he lost against Lloyd Harris at the Citi Open in Washington D.C.

But Nadal is going to be back into the swing of things in the next month. The Melbourne 250 starts on January 4 and will serve as a warm-up for the Australian Open.

Gael Monfils is headlining the ATP 250 event in Adelaide during the same week, while Novak Djokovic – whose participation at the Australian Open is as of yet unclear, although he is also listed for entry – is set to lead Serbia at the ATP Cup in Sydney. 

Djokovic has not yet revealed his COVID-19 vaccination status. If he is not fully vaccinated, the 34-year-old may not be able to compete in Melbourne, barring a medical exemption.

Nadal has dropped down to world number six after another injury-hit season, in which he won two titles, triumphing in Barcelona and Rome.

He has only won the Australian Open once, in 2009, but has since been beaten four times in the final, in 2012, 2014, 2017 and 2019.

Since the start of the 2020 season, Nadal has played in four finals, winning them all, including last year's delayed French Open.

World number one Novak Djokovic has committed to playing the ATP Cup in Sydney amid ongoing uncertainty over his title defence at next month's Australian Open.

Djokovic has been unwilling to confirm his place at January's Australia Open due to the COVID-19 mandate in Victoria.

The state of Victoria, where the year's opening grand slam takes place at Melbourne Park, has introduced a vaccine mandate for professional athletes and across most industries due to the coronavirus pandemic.

Djokovic's father, Srdjan, said the nine-time Australian Open champion is unlikely to feature in Melbourne unless vaccination rules are relaxed.

But in a boost for the slam's organisers, Djokovic was named in top-seeded Serbia's team for the third edition of the ATP Cup, which will take place in Sydney from January 1-9.

"We're excited to host the third edition of the ATP Cup in Sydney in 2022," said ATP Cup tournament director Tom Larner.

"The playing group enjoy representing their countries and to see 18 of the world’s Top 20 players commit to the event is testament to that.

"The event shows off the passion the playing group have for this format and we look forward to welcoming all 16 teams to Sydney later this month."

The 2021 Australian Open went ahead, albeit in February instead of January, and without fans for most of the tournament following a snap lockdown of Melbourne due to COVID-19.

Djokovic – winner of a joint-record 20 grand slam titles – was among the players critical of the conditions athletes endured prior to this year's Australian Open, with strict quarantine measures introduced.

Rafael Nadal conceded that Novak Djokovic will likely end his career with the most grand slam singles titles in men's tennis history, ahead of the Spaniard and Roger Federer.

The so-called 'Big Three' of tennis have long dominated the ATP Tour, with all three sitting on 20 major titles after Djokovic collected three from a possible four in 2021.

Djokovic, who secured a year-end number one ranking for a record seventh time, would have completed a clean sweep if it were not for Daniil Medvedev in the US Open final.  

Nadal, by contrast, missed large parts of the season with a foot injury, while Federer was similarly ruled out for a substantial period after requiring a third knee operation in the space of 18 months.

Nadal could make a return for the Australian Open in January, an event that the world number one may miss due to a vaccine mandate, but he still expects Djokovic to hold the record for major titles when the trio has retired.

"Djokovic is best positioned to be the [men's] player with the most grand slams," Nadal said to Movistar.

"You don't have to fool yourself – Federer is where he is and I am where I am. However, Djokovic is playing well and in a good moment.

"That is the reality, and you can't ignore it. We don't know what is going to happen in nine months' time, but he is the favourite right now."

Nadal triumphed at Roland Garros in 2020 but has only appeared at two majors since, while Federer – who hopes to return to tour-level action in 2022 – last collected a grand slam title at the Australian Open in 2018.

Nadal is glad that the likes of Stefanos Tsitsipas, Alexander Zverev and Medvedev, who only dropped one set across the entire tournament as he denied Djokovic the perfect year, are taking over.

"They are no longer the Next Gen, we do not have to make it eternal," Nadal said of the new 'Big Three' in tennis.

"Players like Medvedev, Zverev or Tsitsipas have already passed that stage of the Next Gen, they are the current generation, the present."

Novak Djokovic is unlikely to play at the Australian Open in January unless COVID-19 vaccination rules are relaxed, according to the player's father.

Organisers recently confirmed that players must be vaccinated against coronavirus to compete in the tournament, which begins on January 17.

World number one Djokovic, who won a record ninth title in Melbourne last year, has not publicly stated whether he has had the jab.

Srdjan Djokovic told Serbia's TV Prva that being vaccinated is a personal choice, and that Tennis Australia's rules are essentially "blackmail".

"As far as vaccines and non-vaccines are concerned, it is the personal right of each of us whether we will be vaccinated or not," he was quoted as saying by news website B92.

"No one has the right to enter into our intimacy, it is guaranteed by the constitution. Everyone has the right to decide on their health.

"Whether [Novak] is vaccinated or not, that is his exclusive right. Will he publish it, I don't think so. I don't know that decision either, and if I did, I wouldn't share it with you. He has the right to decide as he wants."

When asked about Djokovic's decision to play in Australia, his father added: "Whether he will appear there depends on how [the organisers] position themselves. He would want it with all his heart because he's an athlete, and we would love that too.

"Under these blackmails and conditions, he probably won't. I wouldn't do that. And he's my son, so you decide for yourself."

Djokovic, who is tied on 20 major singles titles with Rafael Nadal and Roger Federer, recently said he was unsure of his participation following his appearance at the ATP Finals in Turin.

"I was just waiting to hear what the news is going to be and now that I know we'll just have to wait and see," he said.