Novak Djokovic apologised but confirmed he had been dealing with a blister after only playing a set of his exhibition match in Adelaide.

The world number one had reportedly withdrawn and was replaced by Filip Krajinovic for a clash against Jannik Sinner.

But Djokovic played the second set, winning it 6-3 after Krajinovic had taken the opener 6-3 on Friday.

The 17-time grand slam champion, who had a blister on his right hand, apologised after the match.

"I'm sorry that I didn't step in on the court from the beginning," Djokovic told Channel 9.

"I had to do some treatment with my physio and wasn't feeling my best the last couple of days, I didn't know how I'm going to react.

"I wanted to play and I wanted to get out here and hopefully it was enough for you guys to see all three of us performing in front of you on the court today, I hope you enjoyed."

Djokovic, who came out of hotel quarantine on Friday, said he could not pass up the opportunity to play in front of fans.

"It's not easy but it's part of what we do. We are professional athletes we learn over the years to play with the pain and it's just a question and case whether that pain is bearable or not," he said.

"Obviously coming off from the hard training block and having an ATP Cup and Australian Open around the corner you don't want to risk it too much.

"But the emotion was so strong in me to come out on the court today seeing almost full stands, I had to play, that's it, I had to play."

Djokovic is due to play the ATP Cup starting on Tuesday, before the Australian Open begins on February 8.

Andy Murray has withdrawn from the Australian Open a little over a week after testing positive for coronavirus.

Murray, a five-time finalist in Melbourne, went into isolation at home after returning a positive test on January 14.

The three-time major winner, ranked 123rd in the world, had hoped to compete at the first grand slam of the year after being granted a wildcard.

However, tournament organisers indicated it would be difficult for Murray to remain in the draw as he would be unable to travel via one of the official charter flights containing other players before going through the required period of quarantine.

On Friday, the 33-year-old confirmed he had been unable to come to a "workable" solution with authorities.

In a statement carried by The Guardian and other UK media outlets, Murray said: "Gutted to share that I won't be flying out to Australia to compete at the Australian Open.

"We've been in constant dialogue with Tennis Australia to try and find a solution but we couldn't make it work.

"I want to thank everyone there for their efforts, I'm devastated not to be playing out in Australia. It's a country and tournament that I love."

The build-up to this year's Australian Open has been impacted by players having to spend a two-week quarantine in their hotel accommodation.

A total of 72 competitors have been unable to leave their rooms after positive coronavirus tests among passengers on the chartered flights to Melbourne.

Players have been unable to access practice courts and many have complained on social media about sub-standard food and conditions, with Yulia Putintseva, the world number 28, sharing videos showing mice in her room.

The tournament is due to start on February 8.

Tennis umpire Carlos Bernardes is "recovering well" after reportedly suffering a heart attack ahead of the Australian Open.

The veteran Brazilian, who has officiated in US Open and Wimbledon men's singles finals, was taken from his hotel to a Melbourne hospital on Wednesday after falling ill.

It was widely reported he had a heart attack, with Bernardes pictured on a stretcher while being loaded into an ambulance.

The ATP, which runs the men's tour and has been Bernardes' employer since 1990, offered an positive update on Thursday.

In a statement, the governing body said: "Following admittance to hospital [non-COVID related] on Wednesday in Melbourne, we are pleased to report that ATP umpire Carlos Bernardes is recovering well.

"Carlos passes on his gratitude for all the well wishes he's received, and we wish him all the best for a full recovery."

According to Brazilian tennis website TenisNews, Bernardes remains under observation but is expected to leave hospital on Saturday.

He was staying at The View, one of three hotels where Australian Open players and tennis officials are quarantining for two weeks after their arrival in the country.

Novak Djokovic has denied he was being "selfish, difficult and ungrateful" in making suggestions for easing quarantine restrictions ahead of the Australian Open.

Djokovic came in for criticism after it emerged he had sent Australian Open tournament director Craig Tiley a list of potential ways for lockdown conditions to be improved for players who are under a strict lockdown in Melbourne.

Less than three weeks before the first major of the year gets under way, 72 players are consigned to their hotel rooms due to positive coronavirus tests on their flights to Melbourne.

World number one Djokovic does not have to adhere to such stringent rules in Adelaide, as he arrived on a virus-free flight.

The 17-time grand slam champion was labelled a "tool" by Nick Kyrgios after he was said to have asked for less time in isolation for players, requested they are given private housing with access to training courts, and better food.

Djokovic responded on Wednesday by stating that he was only trying to look out for his fellow players and expressed his gratitude to tournament organisers, the Australian government and the people of Melbourne.

He posted on social media: "My good intentions for my fellow competitors in Melbourne have been misconstrued as being selfish, difficult and ungrateful. This couldn't be farther from the truth

"I genuinely care about my fellow players and I also understand very well how the world is run and who gets bigger and better and why.

"I've earned my privileges the hard way and for that reason it is very difficult for me to be a mere onlooker knowing how much every help, gesture and good word mattered to me when I was small and insignificant in the world pecking order.

"Hence I use my position of privilege to be of service as much as I can where and when needed."

The Serb added of his correspondence with Tiley: "In our email exchange I used an opportunity to brainstorm about potential improvements that could be made to the quarantine of players in Melbourne that were in full lockdown.

"There were a few suggestions and ideas that I gathered from other players from our chat group and there was no harm intended to try and help.

"I was aware that the chances were low that any of our suggestions would be accepted, just like my request to quarantine with my team in Melbourne instead of Adelaide was denied prior to our travel because of the strict government regulations.

"I understand that organising international sporting events during a pandemic poses health risks to the local community and to the players themselves.

"Therefore, I would like to express my full gratitude to Tennis Australia, the Australian Government and local citizens for being willing to take this risk with us for the love of the game and the multiple opportunities it brings to the economy of the country and its people.

"We are honoured and we will all do our best to follow the guidelines and protocols put in place. We do hope that we will be able to nurture our bodies and be ready for the mental and physical endurance and strength tests that are ahead of us once the competition starts.

"Things in the media escalated and there was a general impression that the players [including myself] are ungrateful, weak and selfish because of their unpleasant feelings in quarantine. I am very sorry that it has come that because I do know how grateful many are.

"We all came to Australia to compete. Not being able to train and prepare before the tournament starts is really not easy. None of us ever questioned 14 days of quarantine despite what is being said by media outlets."

Victoria Azarenka called for greater understanding from players stuck in hotel quarantine ahead of the Australian Open.

After being exposed to coronavirus on flights, 72 players – including Azarenka – have been forced into a two-week quarantine ahead of the tournament beginning on February 8.

Novak Djokovic reportedly made several requests, which were rejected, of officials for players in quarantine, while Roberto Bautista Agut compared the conditions to prison.

But amid complaints on social media, two-time Australian Open champion Azarenka pleaded for players to be more understanding in a measured statement.

"Dear players, coaches, entourage and Australian community. I would like to take a moment and address some of my colleagues as well as the media around the world," the Belarusian wrote on Twitter.

"This has been a very difficult time for a lot of us that did not expect to end up in the situation we are in today, myself included. To be in a 14-day hard quarantine is very tough to accept in terms of all the work that everyone has been putting in during their off-season – to be prepared for playing our first grand slam of the year. I understand all the frustration and feeling of unfairness that has been coming and it is overwhelming.

"We have a global pandemic, nobody has a clear playbook of how to operate at full capacity and without a glitch, we all have seen it last year. Sometimes things happen and we need to accept, adapt and keep moving.

"I would like to ask all my colleagues for cooperation, understanding and empathy for the local community that has been going through a lot of very demanding restrictions that they did not choose, but were forced to follow.

"I would like to ask to be sensitive as well to the people who have lost their jobs and loved ones during this horrible time for all of us around the world. I would like to ask all of us to have respect for people who work tirelessly to try to make our lives easier.

"I would like to ask the media to please have consciousness on the impact and influence you bring to this situation and to the community. I would like for the people in the community to know and understand that we have it as our top priority to ensure the health [and] safety of all the people.

"Lastly, I would like for us to please try to support each other as much as someone can or is willing to. Things are always easier when you have a compassionate environment and work together."

Victoria endured tough restrictions after a second coronavirus wave last year.

On Tuesday, the state recorded its 13th consecutive day of no locally acquired cases of COVID-19.

Roberto Bautista Agut labelled the quarantining of players ahead of the Australian Open a "complete disaster", comparing it to prison.

After being exposed to coronavirus on flights to Australia, 72 players are in hotel quarantine for two weeks ahead of the tournament starting on February 8.

Players have hit out at the conditions, although tournament director Craig Tiley insisted on Tuesday most were happy to be in Australia.

But world number 13 Bautista Agut slammed the position players had been put in.

Told he looked like he was in prison, the Spaniard told Sport5: "It's the same, it's the same, with Wi-Fi.

"These people have no idea about tennis, about practice courts, has no idea about anything, so it's a complete disaster because of that, because the control of everything.

"It's not Tennis Australia, it's the people from the government."

Victoria on Tuesday recorded its 13th consecutive day of no locally acquired coronavirus cases, with three of the four in hotel quarantine linked to the Australian Open.

Bautista Agut, a 2019 quarter-finalist at Melbourne Park, said two weeks in quarantine would be difficult.

"I did work in the room but it's not the same," he said.

"I was feeling very, very tight and I cannot imagine staying two weeks like this. It's really, really tough."

Australian Open tournament director Craig Tiley defended Novak Djokovic, saying the world number one had provided "suggestions", not demands.

With 72 players forced into quarantine for two weeks after being exposed to coronavirus on flights, Djokovic reportedly made demands regarding their conditions.

Among them, the eight-time Australian Open champion reportedly asked for players to be moved to private houses with tennis courts, with his requests rejected.

But Tiley played down the reports, saying Djokovic had simply made suggestions.

"Novak wrote a note, these weren't demands, these were suggestions," he told Channel 9 on Tuesday.

"But he too is understanding what two weeks of lockdown means."

Tiley also backed the players despite reports and social media posts suggesting they were unhappy about being forced into quarantine.

"Last night we spent quite a bit of time with the playing group going through a number of different items because they've just been here for a few days getting used to this quarantine environment," he said.

"I have to say on that call there were about 500 players and the vast majority are happy to be here, pleased to be here and really getting ready in the next two weeks to be able to get out and play in the lead-in events and then play the Australian Open on February 8.

"I think the reports we're reading and the things we're seeing doesn't represent the entire playing group. For the most part, they've been pretty good."

With the preparations of 72 players so far impacted by quarantine, there have been suggestions the Australian Open be changed to a best-of-three sets format in the men's draw.

But Tiley said he had no plans to make such a drastic change.

"We're a grand slam at the end of the day and right now three out of five sets for the men and two out of three sets for the women is the position we plan on sticking to, starting February 8," he said.

Nick Kyrgios has labelled Novak Djokovic "a tool" after the world number one reportedly issued a list of demands for players under strict quarantine conditions ahead of the Australian Open.

Defending women's singles champion Sofia Kenin is among 72 players who are consigned to their hotel rooms due to positive coronavirus tests on flights they took to head out for the first grand slam of the year.

Players have posted social media clips of them training and in their rooms, with some complaining about the conditions they are having to contend with for 14 days.

Bernard Tomic's girlfriend, Vanessa Sierra, expressed her grievances over the standard of food and having to wash her own hair and dishes during her period of quarantine with the world number 228 so far.

Djokovic does not have to adhere to such strict rules in Adelaide, where he is due to play in an exhibition tournament before the Melbourne major, as he arrived on a virus-free flight.

Yet the 17-time grand slam champion is said to have asked for less time in isolation for players, requested they are given private housing with access to training courts, and better food.

Kyrgios tweeted on Monday: "Djokovic is a tool. I don't mind Bernie [Tomic] but his Mrs obviously has no perspective, ridiculous scenes Man."

Three weeks before the Australian Open is due to get underway, Victorian premier Daniel Andrews said the players will not be getting any "special treatment."

He said: "The virus doesn't treat you specially, so neither do we.

"I know there's been a bit of chatter from a number of players about the rules.

"The rules apply to them as they apply to everybody else and they were all briefed on that before they came and that was the condition on which they came. So, there's no special treatment here."

A further 25 players have been forced into hard lockdown for two weeks prior to the Australian Open, tournament organisers have confirmed.

Tennis' season-opening grand slam was plunged into crisis on Saturday when it was announced 47 players would be consigned to their hotel rooms for 14 days and not eligible to practise.

Officials said the protocols were as a result of two passengers testing positive for coronavirus on a flight from Los Angeles that arrived on Friday morning, along with another passenger who flew in from Abu Dhabi.

That affected 24 players aboard the LA flight and 23 on the plane from Abu Dhabi, while another positive test for a passenger arriving in Melbourne from Doha on Saturday morning has taken the total number of players affected to 72.

A statement from the Australian Open read: "One positive COVID-19 test has been returned from a passenger on a charter flight into Melbourne from Doha which arrived at 5.30am on January 16.

"The passenger is not a member of the playing contingent and had tested negative before the flight.

"There were 58 passengers on the flight, including 25 players. All are already in quarantine hotels.

"The 25 players on the flight will not be able to leave their hotel room for 14 days and until they are medically cleared. They will not be eligible to practise."

About 1,200 players and staff have been arriving in Melbourne on sparsely populated aeroplanes ahead of the delayed Australian Open, which is due to get under way on February 8.

Speaking on Saturday, Tennis Australia CEO Craig Tiley insisted the tournament would be going ahead despite the chaos and the lack of preparation time for many of the playing contingent.

"It's not something we wanted to happen," he told The Today Show. "We were hoping every flight would be okay. We're in this situation, we have to deal with it.

"The Australian Open is going ahead and we'll continue to do the best we can possibly do to ensure those players, who are not in a great position, find it somewhat acceptable.

"We're planning on February 8, we do have that buffer time in there. We're looking forward to welcoming fans to the Australian Open.

"Ticket sales have been going well, we've got two weeks of great tennis and our intention is to continue with those dates."

The Australian Open has hinted Andy Murray will not be able to compete in Melbourne following his positive test for coronavirus.

Murray, a five-time finalist at the Australian Open, remains in good health and is isolating at home.

The three-time grand slam winner is still hoping to play and travel to Australia later than planned.

However, a statement from the tournament cast serious doubt on his involvement, with Murray – ranked 123rd in the world – having initially been granted a wildcard to play.

The statement read: "Andy Murray has advised that he has tested positive for COVID-19 and is isolating at home in the UK.

"Unfortunately, this means that he will be unable to join the official AO charter flights arriving in Australia in the coming days to go through the quarantine period with the other players.

"The AO fans love Andy, and we know how much he loves competing here in Melbourne and how hard he'd worked for this opportunity."

The first grand slam of the year is starting three weeks later than it normally would on February 8 due to the complications of players flying into Australia amid the ongoing coronavirus pandemic.

Tournament organisers are putting on 15 chartered flights, which will operate at 25 per cent capacity, to bring players to the tournament.

Before boarding, competitors must test negative and will undergo a series of tests once in the country, while undergoing a 14-day quarantine period in Melbourne.

It was after a first-round defeat at the Australian Open two years ago that Murray stated his career might be over due to an ongoing hip injury.

Andy Murray's participation at the Australian Open is in doubt following a positive COVID-19 test.

Three-time grand slam champion Murray remains in good health but is isolating at home.

The 33-year-old Briton is still hopeful of being able to travel to Australia later than planned and taking part in the first grand slam of the year.

Murray received a wildcard for the Australian Open, where he has been a runner-up on five occasions.

It is set to be the Briton's first participation at Melbourne Park since announcing after a first-round loss in 2019 that his career was in the balance due to a persistent hip injury.

The Australian Open is scheduled to get under way on February 8.

Rafael Nadal will be without his coach Carlos Moya due to the pandemic, while Dominic Thiem's coach Nicolas Massu tested positive before travelling to Australia.

It is still hoped that Massu can make the trip following a negative result.

Tennys Sandgren was cleared to board a flight from the United States bound for Melbourne ahead of the Australian Open despite revealing he returned a new positive coronavirus test this week. 

The American, twice a quarter-finalist at Melbourne Park, initially posted to social media on Wednesday that he had tested positive for the virus for a second time. 

Although his first instance of having the illness was recorded in November, the 29-year-old's participation in the tournament appeared to be in doubt. 

But, as he continued to update followers through the day, it emerged he had been allowed to board his flight. 

Writing on Twitter, he said: "Wait hold on I think they are trying to get me on 15 min [sic] after the plane was supposed to depart.. my bags still aren't checked lol." 

A follow-up read: "Wow I'm on the plane. Maybe I just held my breath too long. Craig Tiley [Tennis Australia] is a wizard." 

Some expressed concerns about the possibility of Sandgren potentially spreading the virus to fellow passengers and then locals once he arrives in Australia. 

But a statement from the Australian Open has looked to reassure people that players' infectiousness is checked prior to boarding flights. 

It read: "In the case of Tennys Sandgren, who has self-disclosed that he previously tested positive in late November, his medical file had to be reviewed by Victorian health authorities. Upon completion of that review he was cleared to fly.

"Any recovered case must go through this process in order to have an opportunity to travel here for the Australian Open. No one can travel without either proof of a negative test or this special clearance from authorities confirming they are not infectious. 

"Upon arrival all players are immediately placed in a secure quarantine environment for 14 days under the authority of COVID Quarantine Victoria, and will undergo a more rigorous testing schedule than most returning travellers." 

An earlier statement issued by the tournament organisers in reply to Sandgren's tweets said: "Some people who have recovered from COVID-19 and who are non-infectious can continue to shed the virus for several months. 

"Victorian Government public health experts assess each case based on additional detailed medical records to ensure they are not infectious before checking in to the charter flights. 

"Players and their teams are tested every day from their arrival in Australia, a much stricter process than for anyone else in hotel quarantine." 

The first grand slam of the year is due to begin on February 8 after being delayed due to the pandemic. 

Initially it was to run from January 18-31 but was pushed back to help give qualifiers time to travel and complete a two-week quarantine in Australia prior to warm-up events getting under way at the end of the month. 

Players at Melbourne Park will have to follow strict guidelines and protocols, including a five-hour limit on training with a maximum of one team member. 

The teams must stay in their hotel for the other 19 hours of every day, and players have to return six negative COVID-19 tests before being allowed to play.

Alexander Zverev insists his latest split from a high-profile coach ended on amicable terms after David Ferrer cut ties with the US Open finalist.

Spaniard Ferrer's decision to walk away leaves Zverev yet again, now at the age of 23, looking for a coach with whom he might establish a long-term partnership.

The German ditched former world number one Juan Carlos Ferrero in early 2018, after six months together, claiming the coach had been "very disrespectful" to other members of his team.

He then linked up with Ivan Lendl in August 2018 but that lasted just under a year, with Zverev reportedly criticising the eight-time grand slam winner's focus.

This time, Zverev and former world number three Ferrer have not hinted at any animosity or disagreements.

They teamed up in July 2020, and Zverev said of their break-up: "I would like to thank David for the months we have shared, the times on and off the court, wishing him only the best in the future.

"I also want to thank his family for giving me the chance to spend precious weeks with David during these difficult times. I have tremendous respect for the way David played and coaches tennis."

Ferrer helped Zverev battle through to the US Open final in September, where he led by two sets but was ultimately beaten by Dominic Thiem.

Zverev also won a pair of titles in Cologne in October and reached the final of the Masters 1000 event in Paris.

But they are going their separate ways as the new season begins, with the Australian Open just weeks away.

Ferrer said: "At the end of the year, a decision had to be made, I spoke with Sascha [Zverev] and told him that I preferred not to continue, that we were not going to continue next season. Not for anything special, I just didn't think it was time."

Speaking to tennis website Punto de Break, Ferrer added: "Absolutely nothing has happened between us, everything is still fine, in fact I am very grateful to him for the opportunity he gave me to travel with him during that stretch of the season.

"During those months we had a good coexistence, everything was perfect."

Roger Federer decided to miss the Australian Open because wife Mirka opposed having to spend a full fortnight in quarantine, a leading official has claimed.

It was widely assumed Federer's reason for skipping the upcoming grand slam related to the knee surgery he underwent last season.

He had hinted as much, and agent Tony Godsick referred to the knee rehabilitation when announcing in December that the Swiss great would not travel to Melbourne.

But Andre Sa, the head of player liaison at Tennis Australia, says Federer pulled out when it became apparent his wife and children would be holed up in their hotel accommodation for two weeks.

The players travelling to Australia must all quarantine to avoid any possible spread of COVID-19, but they are allocated five hours per day in which they can leave their rooms to train and practise with specified hitting partners.

Sa, a former top-20 doubles player, told Band Sports in his native Brazil that he discussed with father-of-four Federer the practicalities before the 20-time grand slam winner reached his decision.

"The main reason was the quarantine," said Sa. "I talked to him a month ago and he had two options. He could come with the whole family and do the quarantine.

"The problem is that Mirka and her children couldn't leave the room. They would have to stay 14 days in the room. The exception is only for players.

"He could go out, train and come back, but the family couldn't. Mirka did not approve the idea.

"The other option would be for him to come alone. Only there would be at least five weeks away from family and children. And then he said, 'Dude, 39, four kids, 20 grand slams. I'm no longer at the stage to be away from my family for five weeks.'"

Former world number one Federer has not played a tournament since losing to Novak Djokovic in the semi-finals of the Australian Open last year.

This year's edition of the grand slam has been delayed by three weeks to a February 8 start, due to factors tied into the pandemic.