World number one Ash Barty won her first WTA Tour match in almost a year at the Yarra Valley Classic, while Naomi Osaka got her Gippsland Trophy campaign going with a victory.

Barty sat out the vast majority of the 2020 season due to the coronavirus pandemic but marked her comeback with a 6-3 6-3 success over Ana Bogdan at Melbourne Park.

The Australian will face Marie Bouzkova next after the Czech defeated Aliona Bolsova on Tuesday.

Garbine Muguruza raced past Alison Van Uytvanck 6-2 6-0 and she was joined in the third round by Petra Kvitova, who battled to beat Venus Williams 7-6 (8-6) 7-5.

Reigning Australian Open champion Sofia Kenin, who was 7-5 up when Camila Giorgi retired from their match, is also through.

In her first match since winning the US Open in September, Osaka cruised to a 6-2 6-2 success against Alize Cornet and will meet Katie Boulter after the Briton came from a set down to beat Coco Gauff 3-6 7-5 6-2.

Iga Swiatek was also making her first appearance since winning a major title – the French Open last October – and after a slow start won 10 of the final 11 games to beat Kaja Juvan 2-6 6-2 6-1.

Aryna Sabalenka ended 2020 with back-to-back titles in Ostrava and Linz, before kicking off the new year with another trophy in Abu Dhabi. However, her run of 15 straight victories ended with a 1-6 6-2 1-6 loss to Kaia Kanepi.

Bianca Andreescu was due to gear up for the Australian Open by contesting the Grampians Trophy this week but withdrew from the competition to focus on training instead.

Serena Williams and Simona Halep started the season with straight-sets victories in Melbourne a week before the Australian Open gets under way.

Williams and Halep played in an exhibition event with a crowd of 4,000 watching on in Adelaide last Friday and they were back in competitive action three days later.

Legendary American Williams beat Daria Gavrilova 6-1 6-4 to move into the third round of the Yarra Valley Classic.

The fifth seed struck 27 winners to 15 unforced errors on Margaret Court Arena as she set up a meeting with Tsvetana Pironkova, who ousted Donna Vekic 1-6 6-4 6-2.

Williams said: "It was a good match for me. It wasn't easy at all. It was lots of rallies and lots of movement, and she's from here, so she obviously always plays hard. So it was really good and it felt good to clinch that in the end."

Third seed Karolina Pliskova, Petra Martic, Danielle Collins and Marketa Vondrousova also advanced to the last 16 on Monday.

Elsewhere, top seed Halep is through to the third round of the Gippsland Trophy following a 6-4 6-4 win over Anastasia Potapova.

Halep hit 23 winners and broke twice in each set in what was her first official match since October.

Elina Svitolina, the third seed, beat Andrea Petkovic 6-1 6-4, while Coco Gauff, Ekaterina Alexandrova and Jelena Ostapenko were among the other winners seven days prior to the start of the first grand slam of 2021.

Naomi Osaka would be prepared to spend another two weeks in quarantine to be able to play at a "very special" Olympics in Tokyo.

Postponed due to the coronavirus pandemic, the Games are scheduled to begin on July 23 this year.

This year's Australian Open will begin on February 8 after players quarantined ahead of the first grand slam of the year.

Osaka said she would be prepared to do it all again if it meant she got the chance to play at the Olympics.

"Honestly, my concern isn't the athletes. The way that I feel is I will stay in my room for two weeks to play the Olympics. I missed out on the last one," the Japanese star told a news conference on Sunday.

"Playing in Tokyo would be very special to me. My concern would be the general safety of everyone else because you're opening the country.  Everyone is flying in from different places. I would just want the public to feel safe.

"I feel like the athletes definitely would want to play, but I would want the public to feel safe."

Doubts have also been cast over the Olympics going ahead this year due to COVID-19.

Osaka, a three-time major champion, said while people she had spoken to were excited, some were worried.

"For me the people that I've spoken to, they're really excited about it, but they're concerned because, I don't know, there's just like so many different people entering. I don't know," she said.

"For the people I've talked to, they said as long as everyone is safe, as long as Japan is getting better and not worse, then it should be okay.

"But for me, hmm, don't quote me on that."

Ahead of the Australian Open, Osaka is playing the Gippsland Trophy, where she will face either Alize Cornet or Ajla Tomljanovic in the second round.

The Australian Open is set to welcome up to 30,000 spectators each day when the tournament begins on February 8 in Melbourne.

Local officials have given the go-ahead for fans to head to Melbourne Park, predicting a near-normal atmosphere when action begins at the year's first grand slam.

Last year's US Open was contested behind closed doors in New York, while only 1,000 paying fans were allowed at Roland Garros on each day of the 2020 French Open.

However, the COVID-19 crisis has been tightly managed in Australia, to the point where it was reported on Saturday that there had been no new local cases in the state of Victoria for 24 days.

The crowds will be split between day and evening sessions, and the number of fans allowed will drop to 25,000 for the final six days of the tournament, when fewer courts will be in operation.

Saturday's announcement means the event will be capped at around 50 per cent of capacity.

Tournament director and Tennis Australia chief executive officer Craig Tiley said it had taken "a massive team effort" to accommodate the arrival of around 1,000 players and officials into the country, with all required to spend two weeks in quarantine.

Victoria sports minister Martin Pakula said on Sky News Australia: "On Rod Laver Arena, as we get towards the end of the tournament, we'll have an incredible atmosphere – not that different to the atmosphere we've seen in all the Opens in the years past.

"That's really a testament to the work Victorians have done to get our numbers to zero but also the extraordinary work that Craig and the team at Tennis Australia has done."

Serena Williams and Rafael Nadal agreed it was great to be playing in front of busy grandstands again as tennis stars emerged from lockdown in Australia.

The women's and men's tennis tours have been contested largely behind closed doors over the past year, and a number of tournaments, most notably Wimbledon, have been cancelled due to the COVID-19 crisis.

The Australia public has given a cautious welcome to the arrival of the world's leading players, who have been quarantining in hotel rooms for much of the past fortnight, only allowed to briefly leave in order to train.

Ahead of the Australian Open, which begins on February 8 in Melbourne, Williams and Nadal are among a star-studded set of players who travelled to Adelaide to feature in the 'A Day at the Drive' exhibition event.

They both scored victories on Friday, with Williams defeating US Open champion Naomi Osaka 6-2 2-6 10-7 and Nadal snatching a 7-5 6-4 win over Dominic Thiem.

The delight in both at seeing crowds at a tournament was plain, with Williams saying in an on-court interview: "Thanks everyone for having us. We haven't played in front of a crowd in over a year. It's been a really long time."

In fact, it has not quite been a full year since the tours locked down initially, as it was early March when most tournaments began to be called off, with crowds frozen out.

Williams said the reception made the difficult past fortnight, being hidden away from the world, worth the strain for the players.

"This is really cool and then for having us and trusting us with your laws was great," said the 23-time grand slam winner. "We were so excited to be here and it's worth it."

Nadal said he was "super happy" to still be playing at the highest level and back in front of Australian crowds.

The pandemic has been carefully managed to the point where very few have the virus and it is considered safe to allow crowds into sporting events in the country.

Nadal said: "Hopefully this situation will go away quick and we will be able to enjoy fans on court [around the world].

"We're super excited to have fans at the Australian Open and today."

That optimism and excitement was shared by men's world number one Novak Djokovic, who played just one set against Jannik Sinner due to a problem with blisters on his right hand.

Eight-time Australian Open champion Djokovic told fans: "Thank you so much for coming out and making our day and making our year.

"We didn't play in front of this much crowd for 12 months. This is definitely something very special.

"It wasn't easy, obviously, with 14 days being constrained in the room and a few hours to train, but at the end of the day it was worth it because you guys made it very special today for us."

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."

Madison Keys is set to miss the Australian Open after testing positive for coronavirus.

The 2017 US Open runner-up announced on Thursday that she contracted COVID-19 before she was due to fly out for the first grand slam of the year.

Keys did not state she will definitely miss the major, which starts on February 8, but it appears the American will not make the trip to Melbourne.

The American wrote on Instagram: "Hi everyone, I wanted to let you know that I unfortunately tested positive for COVID-19 before I was supposed to fly to Australia.

"I'm very disappointed to not be able to play in the coming weeks after training hard in the off-season and knowing Tennis Australia and the tours did so much to make these events happen.

"I am self-isolating at home and will continue to follow all the necessary health precautions. I look forward to being back on tour next month."

It was revealed earlier in the day that three-time major winner Andy Murray has also tested positive for the virus, but still hopes to play in the Australian Open.

Meanwhile, world number 50 Tennys Sandgren was cleared to board a flight from the United States bound for Melbourne 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. 

Players will only be allowed into Australia with proof of a negative test just prior to departure, or with approval to travel as a recovered case at the complete discretion of an Australian government authority.

Anyone wanting to travel out for the tournament who previously tested positive is required to provide additional and highly detailed medical information as proof they are a recovered case and no longer infectious or a risk to the community.

Aryna Sabalenka is keen to continue her hot streak after claiming a third consecutive title on the WTA Tour with a commanding victory over Veronika Kudermetova at the Abu Dhabi Women's Tennis Open.

Following season-ending triumphs in Ostrava and Linz, the world number 10 extended her ongoing winning run to 15 matches, prevailing 6-2 6-2 in an hour and five minutes.

"I'm really happy to keep winning and I’ll do everything I can to keep winning," Sabalenka told reporters. "Nobody likes to lose!"

"Every final is really something special and I would say finals are a different competition.

"This final was really nice and I would say a really fast game."

The pace of the contest owed much to Sabalenka's power game, with the Belarusian hitting 18 winners to her opponent's 13, while Kudermetova leaked 24 unforced errors to 13.

Sabalenka's clinical confidence was in evidence as she dispatched six of 12 break points fashioned.

"I’m really proud that I was fighting no matter what," she said of a run that has now yielded titles seven, eight and nine of her career.

"Some matches, I didn't feel my serve, some matches I didn't feel my forehand or backhand, but I would just keep fighting, finding my shots, and that this is what I’m really proud of, and really happy with this title."

Aryna Sabalenka will face Veronika Kudermetova in the Abu Dhabi Women's Tennis Open after extending her magnificent career-best winning run with a straight-sets victory over Maria Sakkari.

Sabalenka ended 2020 in red hot form and has carried on where she left off at Zayed Sports City International Tennis Centre to stand on the brink of claiming a third successive title.

The fourth seed from Belarus has now won 14 consecutive matches following a commanding 6-3 6-2 success over Sakkari on Tuesday.

Sabalenka reached the 13th WTA singles final of her career at the age of only 22, taking just 57 minutes to see the back of ninth seed Sakkari.

The world number 10 struck 22 winners, eight of which were aces, and made only eight unforced errors, while winning 83 per cent of points on her first serve and will be one to watch at the Australian Open next month.

Kudermetova will be playing in her maiden WTA singles final following a 7-6 (10-8) 6-4 victory over Marta Kostyuk of Ukraine.

Russian Kudermetova came from a break down in the first set and was behind in the tie-break, but dug deep to edge in front in a battle between two unseeded semi-finalists.

The world number 46 broke Kostyuk three times in the second set to secure her spot in the championship match, in which she will have to improve on a first-serve percentage of just 46.5.

The top two seeds are both out at the Abu Dhabi Women's Tennis Open after Sofia Kenin and Elina Svitolina suffered quarter-final defeats on Monday.  

Kenin had won the two previous meetings against Maria Sakkari and appeared on course to retain her 100 per cent record when cruising through the opening set.  

However, Sakkari hit back to stun the top seed, dropping just two more games as she rallied in emphatic fashion to triumph 2-6 6-2 6-0 after one hour and 23 minutes on court.  

"I think I did way too many errors and I was hitting too big when I didn't have to. But I'm glad that once again I found the way to turn the match around," the ninth seed told reporters.

Next up for Sakkari will be Aryna Sabalenka, who extended her impressive winning run to 13 matches after coming through a three-set tussle with Elena Rybakina.  

The fourth seed has not lost since going out at the 2020 French Open to Ons Jabeur - a result she avenged when the pair met on Sunday in the last eight in Abu Dhabi.  

In the other half of the draw, Veronika Kudermetova once again got the better of Svitolina, ending the second seed’s hopes of success in the tournament. 

Russian Kudermetova – who won their only previous meeting on the WTA Tour – came out on top in the deciding tie-break to triumph 5-7 6-3 7-6 (7-3).  

She will take on another player from Ukraine next, Marta Kostyuk overcoming a nightmare opening set to beat Spaniard Sara Sorribes Tormo 0-6 6-1 6-4 and reach the last four.