Jessica Pegula said she "can't be more confident" after upsetting Elina Svitolina to reach her first grand slam quarter-final and Ash Barty stayed in the hunt for Australian Open glory on Monday.

Pegula, the daughter of NFL and NHL franchise owners of the Buffalo Bills and the Sabres, beat fifth seed Svitolina 6-3 3-6 6-3 on Rod Laver Arena to set up a showdown with her fellow American and friend Jennifer Brady.

Brady made it all the way to the semi-finals of the US Open last year and has now put together her best run at Melbourne Park after seeing off Donna Vekic 6-1 7-5.

World number one Barty has not dropped a set in her home major and started the second week by dispatching Shelby Rogers 6-3 6-4.

The top seed from Queensland's next assignment will be a meeting with Karolina Muchova, who saw the back of Elise Mertens 7-6 (7-5) 7-5.

Muchova, the 25th seed from the Czech Republic, has made it through to her second grand slam quarter-final - having also reached this stage at Wimbledon in 2019 - without losing a set.

Pegula to put friendship to one side

Pegula and Brady are close friends, but they will have to put that to one side when they meet in the quarter-finals.

The world number 61 claimed her first victory over an opponent ranked in the top 10 just over a month after Svitolina beat her in straight sets in Abu Dhabi.

Pegula hit 31 winners to Svitolina's 19 and won 21 points from 29 when she made a trip to the net as she broke new ground at a major

She said: "I can't get more confident, it's my best result yet and I'm playing good tennis. Today was a hard-fought win, so, yeah, feeling pretty good."

Pegula added on the prospect of facing Brady: "We're here to have fun and compete. If I can do it against somebody that I like, that I wouldn't mind if they beat me, hopefully not, but if they did, why not?"

Brady benefited from strict lockdown

Many players understandably struggled during and after being in a strict two-week lockdown in a hotel room following their arrival in Australia.

Brady was among the players who were not allowed out of their rooms for a fortnight, but said she used the situation to recharge her batteries before the first major of the year.

The 22nd-seeded Pennsylvanian said: "I think it was a little bit of a benefit for me, just taking a break from tennis. I had been going non-stop since World Team Tennis in June. I didn't take any time off.

"I was playing from June and then played US Open, the U.S. tournaments, and then went straight to Europe, then finished there and was training in Europe, then went home for Christmas and then came and started in Abu Dhabi.

"So obviously I didn't really feel super fresh mentally coming into Abu Dhabi. And then when I was away from tennis for two weeks, I felt like I wanted to play again to compete and I think that helped me."

Much improved Czech

Muchova had not been beyond the second round of the Australian Open before last week but now has a semi-final spot in her sights.

The 24-year-old was 4-0 down in the opening set as Mertens got off to a flyer but warmed to the task with her battling spirit and positive approach.

Muchova converted five of the six break points she earned on Margaret Court Arena, also coming from a mini-break down in a first-set tie-break.

She struck 25 winners to Mertens' 15 and advanced despite making 31 unforced errors, getting her rewards for throwing caution to the wind.

World number one Ash Barty secured another quarter-final berth at the Australian Open after outclassing Shelby Rogers 6-3 6-4.

It was a Barty party on Rod Laver Arena, where the 2019 French Open champion dominated from the outset to see off unseeded American Rogers in a little over an hour on Monday.

Barty, who appeared in the semi-finals in Melbourne last year to become the first Australian woman to reach that stage since Wendy Turnbull in 1984, raced past Rogers to set up a meeting with Karolina Muchova.

Home hope Barty and Rogers renewed acquaintances behind closed doors in the last 16 after the former won a match tie-break against last year's US Open quarter-finalist en route to claiming the Yarra Valley Classic.

Barty was unstoppable from the start, striking first in the fourth game and breaking for a 3-1 lead after precision play left Rogers helplessly scrambling around the court.

There was a test for Barty after Rogers earned a pair of break points in the seventh game, but the former saved both.

It was the only real challenge in a first set controlled by Barty, who continued where she left off in the second.

While Rogers showed glimpses, Barty – moving freely with all eyes on her heavily strapped thigh – was firmly in the groove as she broke for a 2-1 lead.

Another break followed but there was a blip for Barty, who was broken for the first time when serving for the match at 5-2 in a late Rogers resistance which only delayed the inevitable.

Data Slam: ​Three in a row for Barty
Barty will contest her third consecutive Australian Open quarter-final. Not since Wendy Turnbull in 1984 has an Australian woman enjoyed such a run. Barty is bidding to become the first Australian woman to win the grand slam since 1978.

WINNERS/UNFORCED ERRORS
Barty – 21/16
Rogers – 14/25

ACES/DOUBLE FAULTS
Barty – 5/3
Rogers – 5/1

BREAK POINTS WON
Barty – 3/6
Rogers – 1/3

Serena Williams is moving better than she has in years, according to her coach Patrick Mouratoglou.

Williams, 39, has looked in good form at the Australian Open as she eyes a record-equalling 24th grand slam singles title.

The American has dropped just one set on her way to the quarter-finals, in which she faces Simona Halep on Tuesday.

Mouratoglou said Williams' movement was the best it has been in several years.

"First of all, it's something that we have put the emphasis on because in tennis that's probably one of the most important things. If you are late on the ball, you can't do what you want to do. Sometimes you don't even touch the ball," he told a news conference on Monday.

"It's a sport where you have to be able to move fast from side to side and long enough. It's something that probably in the last two, three years, this had consequences for Serena.

"Even more, when you're not in a good day, you need a plan B. To be able to have a plan B, you have to be able to move well. If you can't move well, there is no plan B. The only plan is attack.

"I think it cost her a few important matches. So we have decided to find a way to bring back the footwork that she used to have in the past. I feel like she's done a great job. She's moving much better."

Williams last won a major title in Melbourne in 2017, losing four grand slam finals since then.

With all eyes on her as she aims to equal Margaret Court's record of 24 grand slam singles titles, Mouratoglou insisted that mark was not an obsession for Williams.

"Does she need that validation? I don't think she needs that validation.  But, I mean, clearly she came back to tennis to win some other grand slams, so that's for sure the goal," he said.

"Now, she's not as obsessed with the 24 than most of the people in the tennis world, but definitely she wants to win grand slams. That's the only reason why she came back to tennis."

Simona Halep set up a quarter-final duel with Serena Williams after showing admirable character to battle back from a set down to beat Iga Swiatek 3-6 6-1 6-4 and seal her 100th grand slam match win.

Halep and Swiatek put on a thrilling show in the night session on Sunday, as the Romanian two-time grand slam champion demonstrated her fighting spirit to come from a set down and reach the last eight.

Swiatek took charge in the first set after saving the first two break points of the contest, eventually putting herself in a commanding position as she won the 10 of the final 11 points of the set, but Halep remained focused as her 19-year-old opponent began to wobble in the second.

Halep then snuffed out any threat of a turnaround by breaking back straight after losing on her own service in the decider and she went on to set up a meeting with Williams, who had overpowered Aryna Sabalenka earlier in the day.

Naomi Osaka also advanced, though she was by no means comfortable, while Hsieh Su-wei beat Marketa Vondrousova in straight sets.

HALEP'S REVENGE

Halep's clash with Swiatek was their first since the French Open last October, when Swiatek ran out a 6-1 6-2 winner and went on to claim her maiden major title.

Revenge was on the cards at Melbourne Park and Halep got the job done impressively, showing her mettle to return from a set down.

"Well, I thought before the match that I have to be a little bit more aggressive than Paris. In Paris I have been very far back, and my ball didn't go through the court," the second seed said. "So, I thought that it's a better chance to go and hit.

"The pressure came from the way I played the last match against her. I just expected a better game from myself, which I did, and I'm really happy about that."

Halep accepts facing Williams will be an entirely different challenge, but she remains confident despite lauding the American a "legend" in her on-court interview.

"Of course it's different, she's the only one with 23 grand slams, so you cannot compare Serena with all of us, because we do not have so many grand slams," Halep added.

"But when I step on the court, it's just another opponent, and always I'm focused on myself more than I focus on who I play. We played so many times. I know what to expect. I will just try to do my game, and I will be confident."

WILLIAMS ON COURSE

All eyes are on Williams yet again, as she hopes to equal Margaret Court's record of 24 grand slam titles – and on the evidence of her latest win, she will take some stopping as she won 6-4 2-6 6-4.

Williams revealed she had to cope with a little off-court stress this week with her clothing line, and Sabalenka certainly kept the pressure up as the 22-year-old took the second set.

But Williams responded well to the seventh seed, who became the first player to take a set off the former world number one. Williams said she remained confident despite that setback.

"Like I said on the court, I just felt like even games that I lost, I was so close to winning. Not all games, but probably most of those games," she said. "I just needed to play better on the big points.  I knew that I could. I still hadn't reached my peak. I was like, 'Okay, Serena, you got this, just keep going.'"

OSAKA RELEASES HER ANGER

Osaka was in a real spot of bother against Garbine Muguruza, but saved two match points.

The 2019 champion Osaka steadied herself and felt more composed after a brief show of frustration, as she struck the ground with her racquet.

Ultimately, she emerged a 4-6 6-4 7-5 victor, and Osaka felt letting frustration get the better of her for a moment helped her cause.

"On the first match point, I was just thinking that I didn't hit a decent serve that entire game, so I should really focus on my serve," he said. "I feel like my serve stats were pretty good that set, so I was just telling myself to do better.

"Then on the second point, when the rally started, I just told myself not to push [the ball] but also don't do something crazy and make a really bad unforced error. I felt the entire match I was overthinking. There was a moment when I got angry and hit my racquet on the ground. I feel like I released a lot of the thoughts that I had. It just made me go more into instinct-based tennis."

She will face Hsieh next, the world number 71 having beaten Vondrousova – ranked 51 places higher – 6-4 6-2.

Serena Williams calmed injured fears after coming through a thrilling back-and-forth against Arnya Sabalenka to reach the quarter-finals of the Australian Open.

Williams, who is pursuing a record-equalling 24th career grand slam and her first major victory in four years, prevailed 6-4 2-6 6-4 after more than two hours on court against seventh seed Sabalenka.

Her struggles during the second set appeared partly attributable to a fall but Williams recovered her poise and the 39-year-old does not expect any ill-effects in a last-eight showdown against either Simona Halep or Iga Swiatek.

"I don't think so. It didn't hurt at all. I didn't roll my ankle, so that was good," she told reporters.

"Yeah, I think it was just dramatic, me being dramatic.

"My first thought was, 'Not another ankle sprain in Australia'. But I knew immediately that it wasn't.

"Then I was more embarrassed than anything. I was like, 'Oh, my goodness'."

Williams moved well throughout the contest, assuaging any lingering concerns over Achilles problems that have dogged her of late - even manging to rally when Sabalenka reeled off three consecutive games from 1-4 down in the decider.

"I've worked really hard on my movement. Yeah, I like retrieving balls. I mean, obviously I like to be on the offense, but I can play defence really well, as well.

"I do get a lot of balls back when I need to. I didn't think about my Achilles. It's so good to not think about it. Oh, my goodness. It's been a problem actually since 2018.

"I just never want that problem again. It feels really good to just play and to run, to not feel that. It's a great relief."

Arguably Williams' greatest inconvenience around the match was not a physical one, after she had to participate in a Saturday conference call to avert an "emergency" at her clothing business.

"Tennis is a lot less stressful. I don't have to manage a team. I do manage a team actually, but it's different," she chuckled. "Even though I am the CEO of my tennis team, it's definitely different.

"I think a part of me loves being on the court because it's free-flowing. It's not like I have to kind of just manage and make sure everyone is able to perform.

"I have a second career and it's fun. One of our main players, our employees, had an emergency. You got to step it up when you got to step it up.

"I was smart about that. I scheduled a call directly after my practice. I was like, 'Okay, I can do it early and still have the rest of the day to relax'.

"And it was during [Williams' daughter] Olympia's nap, so it was perfect."

Ash Barty may have her focus on winning the Australian Open right now but suggested a career change could be on the cards in the future.  

The world number one made sure she will still be competing during the second week of the tournament in Melbourne by beating Ekaterina Alexandrova in straight sets.  

But, having played international cricket for Australia before switching to tennis, could the multi-talented Barty be considering trying another sport?  

Elsewhere in Saturday's action, Karolina Pliskova lost her cool – and also a couple of rackets – as she slipped to defeat against the impressive Karolina Muchova in an empty Rod Laver Arena, with fans not able to be present due to a five-day lockdown in the state of Victoria.

Elina Svitolina had no such problems in her third-round match, while Elise Mertens was victorious in just over an hour against Belinda Bencic. Jennifer Brady ended Slovenian qualifier Kaja Juvan's run in the first grand slam of the year.

AUSSIE RULES, OK? 

After winning 6-2 6-4 without ever needing to be at her peak, Barty was cheekily asked by former doubles partner Casey Dellacqua – now working in the media – whether she may be set to switch paths again, once her tennis career has come to an end.  

Australian rules football was the answer – but Dellacqua maybe got more than she bargained for from her former playing partner during the on-court interview. 

"I thought it was our deal, we're going to AFLW. It's ABCD [the nickname for the pairing from their doubles career]. We come as a package, and I know we will be going to the [Richmond] Tigers that is for sure," Barty said. "You can't go to Carlton. You have to come to the 'Tiges' with me."

Dellacqua replied: "I need to get out there and start practicing some kicking, but you are good. I would love to do that one day." 

For Barty, though, the next challenge facing her is Shelby Rogers, who knocked out 21st seed Anett Kontaveit during the evening session.  

MAKING A RACKET 

A disgruntled Pliskova was not impressed when punished for smashing up a racket during her match with compatriot Muchova. 

Having received a warning when throwing a racket to the floor during the course of the final game in the opening set, the sixth seed then vented her frustration again on another while in the players' tunnel.  

An official witnessed the incident and reported it to chair umpire Alison Hughes, who punished the Czech with a point penalty before she began serving to open the second set.  

"It's off court, I'm allowed to do what I want," Pliskova insisted when querying the decision to the official. She would go on to hold before recording two successive breaks, yet somehow failed to force a decider.  

Muchova rallied from 5-0 down in sensational fashion, winning seven games on the spin to triumph 7-5 7-5 to make it through to the last 16.

CONTRASTING PROGRESS FOR SEEDS

Svitolina has still yet to drop a set in the tournament after overcoming 26th seed Yulia Putintseva by a 6-4 6-0 scoreline.  

The fifth seed was twice down a break in the first set but, after eventually coming out on top to take a 1-0 lead, breezed through the second in a hurry.  

"She has a very different game style from what I played my last two rounds, so it wasn't easy at the beginning to adjust," Svitolina said. "As soon as I was feeling better, I just stepped my game, and it was quite a comfortable win after." 

Next up will be Jessica Pegula, who is through to the fourth round at a slam for the first time in her career after thrashing Kristina Mladenovic 6-2 6-1.  

There was also success for another American in the main draw, Brady defeating Juvan in straight sets. Her reward is a clash with Donna Vekic, the 28th seed having to save a match point before eventually seeing off Kaia Kanepi 5-7 7-6 (7-2) 6-4 after two hours and 38 minutes on court. 

Ash Barty battled back to win both sets against Ekaterina Alexandrova and book a place in the fourth round of the Australian Open. 

The world number one triumphed 6-2 6-4 after one hour and 21 minutes on court, though there was no crowd present to cheer on the home favourite due to the five-day lockdown in place in Victoria. 

Barty admitted that, with fans having been allowed into Melbourne Park earlier in the tournament, there was a different – if not completely unpleasant – atmosphere to proceedings in the evening session on Margaret Court Arena.

"It's very strange, it changes the sound of the court a little bit," the Australian – who played with her left thigh heavily strapped having pulled out of doubles duty on Friday – said during her on-court interview.

"I love the crowd, but I love the sound the ball makes. It feels a bit like practice."

Barty lost her opening service game as she quickly fell 2-0 behind at the start of the contest, though she hit back impressively to take the opener against the 29th seed.

The 2019 French Open champion claimed six successive games, hitting just five winners as the policy of keeping the ball in play paid off thanks to 16 unforced errors from her opponent. 

Alexandrova was more consistent in the second set, leading to a break of serve that she quickly consolidated to make the score 4-2. 

However, the Russian was unable to cling on to her advantage and, when serving to stay in the match, let slip two opportunities to extend proceedings. Barty will next face Shelby Rogers, who knocked out 21st seed Anett Kontaveit in straight sets.

Elina Svitolina said playing behind closed doors at the Australian Open felt "a bit disturbing" after having fans in attendance earlier in the week.

The Ukrainian fifth seed booked her spot in the fourth round in Melbourne with a 6-4 6-0 victory over Yulia Putintseva on Saturday.

But no fans were in attendance on Margaret Court Arena as Victoria started a five-day lockdown due to coronavirus.

Svitolina, who will face Jessica Pegula in the last 16, said she felt the difference.

"It was very different conditions. I played a night match at 7:00 with a good crowd. Now it was completely different. It was for sure a bit disturbing, I would say, in some ways sad," she told a news conference.

"But it is what it is. I had to accept. I had to have a good mindset, not thinking too much about that. I just tried to focus on my game."

Svitolina reached the fourth round in Melbourne for the third time in four years after mixing 18 winners with 20 unforced errors.

But the 26-year-old said the lack of fans meant the third-round encounter felt like a practice match.

"It feels like that. I actually had few thoughts about it today. It feels like this. I tried to convince myself that it's a grand slam and that we are playing an important match. I have to focus on my match," Svitolina said.

"But for sure there's some thoughts and there is I say some low moments that can sneak into the mind. It's what we have to deal with. I'm trying my best to do it."

Naomi Osaka and Garbine Muguruza set up a blockbuster clash at the Australian Open, while Aryna Sabalenka cannot wait to face Serena Williams.

As Williams was tested before winning through, Osaka and Muguruza raced through their third-round outings in Melbourne on Friday.

Osaka and Muguruza dropped just seven games between them to set up what will be their first meeting, which will take place without fans in attendance as Victoria prepares to move into a five-day lockdown beginning on Saturday due to coronavirus concerns.

Sabalenka also progressed and will next face Williams, while Simona Halep cruised through.

OSAKA, MUGURUZA STORM THROUGH

Osaka, the three-time grand slam champion, brushed past fellow seed Ons Jabeur 6-3 6-2 in the third round.

The Japanese star, winner of the Australian Open in 2019, is looking forward to facing fellow major champion Muguruza.

"I've practised with her once, but it was on grass, and I was younger. It was maybe like a couple years ago," Osaka said.

"But I just remember being really impressed by her, and for me, I've watched her win Wimbledon and win the French Open when I was younger, and I've always wanted to have the chance to play her. So for me, this is really exciting."

A finalist at the Yarra Valley Classic last week, Muguruza's strong start to the Australian Open continued with a 6-1 6-1 thrashing of Zarina Diyas.

"I don't think we've played each other before. Just looking forward for a fourth round, a good fourth round, playing the top players," Muguruza – who has lost just 10 games in the first three rounds – said ahead of facing Osaka. "I feel like that's always the right way, you know, a good sign. Just expecting a good match."

JOB DONE FOR SERENA

Williams' bid for a record-equalling 24th grand slam singles title remains on track after overcoming Russian teenager Anastasia Potapova 7-6 (7-5) 6-2.

In her 101st Australian Open match, Williams secured her 90th career victory in Melbourne. The 39-year-old also improved her overall slam record to 360-51 – Martina Navratilova (306-49) is the only other player to pass 300 wins in the Open Era.

Next up for Williams is Sabalenka, who was too good for Ann Li, winning 6-3 6-1 to reach a major fourth round for just the second time in her career and first in Melbourne.

The Belarusian seventh seed is not daunted by the task facing her when she meets the American for the first time.

"I want to get this thrill. Can I say thrill? I said it right. So it's going to be a thrill. But, yeah. I'm going to do everything I can," Sabalenka said.

HALEP THROUGH AS SEEDS CRUISE

Halep reached the fourth round in Melbourne for the sixth time with a convincing 6-1 6-3 win over Russian 32nd seed Veronika Kudermetova.

Awaiting the two-time major winner in the fourth round is Iga Swiatek after the Polish 15th seed got past Fiona Ferro 6-4 6-3.

Swiatek thrashed Halep 6-1 6-2 on her way to the French Open title last year.

Marketa Vondrousova, the 2019 French Open runner-up, reached the fourth round of the Australian Open for the first time after beating Sorana Cirstea 6-2 6-4.

Up next for the Czech 19th seed is Hsieh Su-wei, who battled past Sara Errani 6-4 2-6 7-5 after two hours and 44 minutes.

Errani had won her previous three meetings with Hsieh in straight sets, including winning a set 6-0 - known as a 'bagel' in tennis parlance - in each of those victories.

It meant Hsieh, 35, had a simple plan against the Italian.

"I don't remember when I lose to someone but someone reminded me I eat the bagel every time so I said, 'Okay, I will try to not take any bagel today'," she said.

Naomi Osaka admitted it was "a bit funny" to be deemed an essential worker as the Australian Open goes on.

The year's first grand slam is set to continue without fans from Saturday as Victoria heads into a five-day lockdown amid coronavirus concerns.

Professional athletes have been deemed "essential workers", meaning the Australian Open can continue.

Osaka, who raced into the fourth round with a 6-3 6-2 victory over Ons Jabeur on Friday, said that seemed strange.

Asked how she felt about being described as an essential worker, the Japanese star told a news conference: "Well, I'm not really sure.

"That kind of seems a bit funny. But I don't know, I don't make the rules. I'm just here just trying to have fun."

Three-time grand slam champion Osaka will face Garbine Muguruza in a blockbuster fourth-round clash.

Serena Williams labelled Victoria's five-day lockdown "rough" as the Australian Open prepares to go behind closed doors amid the coronavirus pandemic.

Fans will not be allowed to attend Melbourne Park - where crowds have been capped at 30,000 per day - from 11:59pm (local time) on Friday until Wednesday after the Victorian government announced a new state-wide lockdown to control an outbreak of the UK COVID-19 strain.

Victorian premier Daniel Andrews made the announcement as Williams booked her spot in the fourth round of the Australian Open, where the 23-time grand slam champion overcame Anastasia Potapova 7-6 (7-5) 6-2.

"I didn't know at all until the match was over. I think it's good that I didn't know," seven-time Australian Open champion Williams told reporters when asked about the lockdown.

"It's rough. It's going to be a rough few days for I think everyone. But we'll hopefully get through it."

American superstar Williams added: "It's not ideal. It's been really fun to have the crowd back, especially here. It's been really cool.

"But, you know what, at the end of the day we have to do what's best. Hopefully it will be all right."

Williams - stuck on 23 majors since winning the 2017 Australian Open in pursuit of Margaret Court's all-time record of 24 - was pushed to the limit by Russian teenager Potapova but prevailed on Rod Laver Arena.

The 39-year-old Williams - who has played and won more matches than any other woman in the tournament's history - celebrated her 90th Australian Open victory in her 101st contest.

"It was good to get through that match," said former world number one Williams as seventh seed Aryna Sabalenka awaits in the last 16. "The first set was extremely tight. I was a little tight, but it worked out. Was able to play a little more free in the second set."

The Australian Open will continue without supporters after Victoria announced a five-day lockdown amid the coronavirus pandemic. 

This year's delayed Australian Open had started on Monday with a limited amount of fans - capped at 30,000 per day at Melbourne Park - due to COVID-19 restrictions.

The Victorian government announced a new lockdown on Friday to control an outbreak of the UK coronavirus strain, state premier Daniel Andrews said.

Victoria's new state-wide restrictions will be introduced from 11.59pm on Friday - with reigning men's champion Novak Djokovic still scheduled to close out the day - until Wednesday.

"Any number of other large and small professional sport events, they will function essentially as a workplace," Andrews told reporters. "But they will not function as an entertainment event, because there will be no crowds.

"And the workforce will be the minimum that is needed in order for that to be COVID-safe and safe in lots of other contexts."

In response, the Australian Open released a statement while tournament director Craig Tiley insisted the slam will continue.

"Tennis Australia continues to work with the government to ensure the health and safety of everyone," the Australian Open said in a statement.

"The Victorian government has announced a five day lockdown commencing at 11:59pm on Friday. Australian Open sessions today and tonight will continue as planned with COVIDSafe protocols in place.

"We are notifying ticketholders, players and staff that there will be no fans onsite at the AO for five days, commencing from Saturday 13 February.

"Full refunds will be available for anyone who has tickets for these sessions and they will be advised on how to apply as soon as possible.  

"The AO broadcast-only contingency plan will commence from Saturday 13 February until restrictions are lifted. Play will continue uninterrupted on the broadcast, albeit without spectators onsite."

The Australian Open was due to get underway in January, but the COVID-19 crisis forced the year's first slam to be pushed back until February.

The lead-in tournaments across the ATP and WTA Tours took place behind closed doors in Melbourne.

Serena Williams remains on track to claim a record-equalling 24th grand slam title after overcoming Anastasia Potapova in a hard-fought battle en route to the Australian Open last 16. 

Williams - stuck on 23 majors since winning the 2017 Australian Open in pursuit of Margaret Court's all-time record - was pushed to the limit by Russian teenager Potapova but prevailed 7-6 (7-5) 6-2 in Melbourne on Friday.

Next up for seven-time Australian Open winner Williams is seventh seed Aryna Sabalenka.

Williams - who has played and won more matches than any other woman in the tournament's history - had only lost four times at a slam to a player ranked outside the top 50 and twice to players outside the top 100.

But she was challenged by Potapova in an error-riddled and difficult opening set on Rod Laver Arena, where the unheralded Russian took the match to her superstar opponent.

Williams hit 22 unforced errors to just 12 winners, faced 11 break points as she was broken twice, and saved a pair of set points en route to a tense tie-break.

Maintaining her challenge, Potapova led 4-2 and 5-3 in the tie-break, but Williams was up to the task - closing out the set in 61 minutes.

Potapova, who only broke the American's serve on one occasion in last year's opening-round loss at Melbourne Park, was not deflated following the tie-break and broke Williams in the first game of the second set.

But like the first set, Potapova was unable to hold serve and Williams took full advantage - breaking twice to secure a 16th fourth-round berth in Melbourne.

Data Slam: Williams rolls on in Melbourne
In her 101st Australian Open match, Williams secured her 90th career victory in Melbourne. The 39-year-old also improved her overall slam record to 360-51 - Martina Navratilova (306-49) is the only other player to pass 300 wins in the Open Era.
 

WINNERS/UNFORCED ERRORS
Williams – 19/31
Potapova – 18/28

ACES/DOUBLE FAULTS
Williams – 9/4
Potapova – 2/8

BREAK POINTS WON
Williams – 5/8
Potapova – 3/12

Ash Barty and partner Jennifer Brady withdrew from their doubles clash at the Australian Open amid fitness concerns over the world number one.

Barty is in the spotlight after her thigh was heavily strapped during Thursday's 6-1 7-6 (9-7) victory over fellow Australian Daria Gavrilova in the women's singles.

Australian star and 2019 French Open champion Barty was scheduled to team up with Brady for Friday's doubles contest against Elise Mertens and Aryna Sabalenka, but the duo pulled out in Melbourne.

Barty did play down the severity of the thigh issue after defeating Gavrilova, with 29th seed Ekaterina Alexandrova awaiting in the third round at Melbourne Park.

"The bandage is very big, but that's more just support so that the tape itself doesn't fall off. It's not a very subtle tape job, you often see it on a lot of the girls," Barty told a news conference on Thursday.

"The guys can hide it beneath their shorts a little bit better. Just a little bit of support. I played a lot of matches in the last 10 days after not playing for 12 months, which is natural.  It's more of an assistance than anything else."

Barty added: "It came on early Tuesday, warming up for the match. But, yeah, obviously it's not affecting the way that I can play in any way.

"It's just more giving the leg some assistance to make sure it doesn't get to a point where it's going to affect me."

Last year, Barty became the first Australian woman to reach the Australian Open semi-finals since Wendy Turnbull in 1984.

The most recent finalist from the home nation was Turnbull in 1980, while Chris O'Neil was the last champion in 1978.

Sofia Kenin's title defence came to a shock end in the second round of the Australian Open, where world number one Ash Barty advanced amid injury concerns.

Kenin was looking to become the first woman to defend her crown at Melbourne Park since Victoria Azarenka in 2013, instead, she was a high-profile casualty in warm conditions on Thursday.

Barty, who lost to Kenin in last year's semi-finals in Melbourne, stayed alive with a straight-sets win over fellow Australian Daria Gavrilova.

Former world number one Karolina Pliskova also progressed beyond the second round as fifth seed Elina Svitolina blitzed American sensation Coco Gauff.

KENIN OUSTED IN BOILOVER

The American star arrived at the year's first grand slam with high expectations and looking to become the first woman to go back-to-back at a major since Serena Williams in 2016.

But fourth seed Kenin fell to experienced Estonian Kaia Kanepi 6-3 6-2, having tallied 10 winners and 22 unforced errors in windy conditions in Melbourne - the scene of her breakthrough slam more than 12 months ago.

It was Kenin's first defeat to a player ranked outside the top 50 since going down to then-number 54 Iga Swiatek in the 2020 French Open final.

Asked why she was nervous pre-match, Kenin told reporters: "It's like the outside pressure. I felt really nervous. I haven't felt my game for, I don't know how long, but I haven't really felt my game so well, even in my first round. 

"I played well, but still haven't felt 100 per cent game-wise. It's obviously tough."

STRAPPED THIGH? NO WORRIES FOR BARTY​

Barty's left thigh was heavily strapped amid concerns but the 2019 French Open champion still booked her spot in the third round with a 6-1 7-6 (9-7) win over countrywoman Gavrilova.

The first Australian woman to reach the semi-finals in Melbourne since 1984, following last year's run, Barty gave up a 5-2 lead in the second set before saving two set points in the tie-break.

Reflecting on Kenin's surprise exit, Barty talked up the standard of the WTA Tour.

"There are no easy matches," said Barty, who next meets 29th seed Ekaterina Alexandrova for a spot in the round of 16. "There are no easy matches in any tour event, any slam, anything. I think every time you walk on the court, you have to try and be able to bring your best tennis to be able to compete with everyone. 

"That's just the level that there is now on the women's side. That's something really exciting about women's tennis now, is that every single match, it's a fair match. You go out there, you play hard, you try to do the best that you can."

PLISKOVA AVENGES LOSS, SVITOLINA TOO GOOD FOR GAUFF

Beaten by Danielle Collins in the third round of the Yarra Valley Classic just eight days ago, sixth seed Pliskova got the better of the 2019 Australian Open semi-finalist this time around.

Pliskova - also a semi-finalist at Melbourne Park two years ago - defeated Collins 7-5 6-2 and next plays 25th seed Karolina Muchova.

"I just played better in some moments, which I didn't last week. Then she was not playing that well as she did last week," Czech star Pliskova said. "I knew if I at least maintain little bit, just play at least similar as I was playing last week, I knew it's going to be difficult for her to repeat what she played last week. I think she really played great."

Owning a 6-1 record in the second round at Melbourne Park - falling only at this stage in 2016 - Svitolina produced a mature performance to conquer 16-year-old star Gauff 6-4 6-3 on centre court as 26th seed Yulia Putintseva awaits. 

Elsewhere, seeds Belinda Bencic, Elise Mertens, Anett Kontaveit, Jennifer Brady and Donna Vekic moved through.