World number one Ashleigh Barty overcame a jittery start to defeat in-form Elena Rybakina 6-3 6-2 and reach the Australian Open fourth round.

Home favourite Barty was broken in her first two service games, but broke back on both occasions before breaking again in the sixth game of the first set.

Kazakh Rybakina, the champion in Hobart last week, converted only two from 10 break points.

Barty will now face American 18th seed Alison Riske in the last 16.

Riske beat Barty's doubles partner Julia Gorges 1-6 7-6 (7-4) 6-2.

"It was a very tough one," the 23-year-old said. "I felt like I had to be switched on. Some of the games were long. It's probably the best I played this summer so far.

"It's nice to have another chance to come out and enjoy it. I'm loving every minute."

Riske beat Barty in the fourth round at Wimbledon in 2019 in what was Barty's first Grand Slam as world number one.

Last year's beaten finalist, Petra Kvitova, comfortably saw off Russian Ekaterina Alexandrova 6-1 6-2. The Czech will play Greek 22nd seed Maria Sakkari, who defeated American 10th seed Madison Keys 6-4 6-4 to reach the fourth round of a Grand Slam for the first time.

Defending champion Novak Djokovic took only 85 minutes to defeat Yoshihito Nishioka 6-3 6-2 6-2 and reach the fourth round of the Australian Open.

The second seed was ruthless with his serving and also efficient, breaking the Japanese world number 71 five times from six opportunities.

"This was one of my best serving matches," said the Serb.

Djokovic will play Diego Schwartzman after the Argentine 14th seed beat Dusan Lajovic 6-2 6-3 7-6 (9-7).

The former world number one lost only one point on his own serve in the opening two sets against 24-year-old Nishioka, and he won 93% of points on his first serve.

The 16-time major winner, 32, said he hoped to carry that form into the next match.

He added: "Schwartzman is one of quickest on the ATP Tour. He's right-handed so I'll have to have different tactics.

"If my serve is good as it was today then I've got a pretty good chance."

Djokovic paid tribute to former Wimbledon champion Goran Ivanisevic, part of his coaching set-up since last year, for helping improve his action.

"Obviously there are a lot of technical details you can talk about - although sometimes less is more," he added. "It's all about the rhythm and balance, to find the contact point on the serve."

Former world number one Caroline Wozniacki saw her hugely impressive career come to a close as she went out in the Australian Open third round.

Wozniacki, 29, revealed her intention to retire in November, fittingly calling time at the venue where she won her only Grand Slam title.

Now ranked 36th, Wozniacki's 15-year career ended with a 7-5 3-6 7-5 defeat by Tunisia's Ons Jabeur.

"It has been a great ride," said the emotional Dane on Melbourne Arena.

"It is fitting my last match would be a three-setter, a grinder, and I'd finish my career with a forehand error - those are the things I have been working on my whole career," joked Wozniacki.

"I guess it was meant to be."

Wozniacki bows out having spent 71 weeks as the world number one, lifted 30 WTA titles and accumulated almost £27m of prize money.

Most significantly, she will always have that coveted Grand Slam title next to her name in the history books.

That came at the third time of asking, following two US Open final defeats, when she beat Simona Halep in the 2018 final at Melbourne Park to complete her "dream".

Wozniacki was diagnosed with rheumatoid arthritis in 2018, although she has said that was not the sole reason behind her decision to retire.

She will "work on" the autoimmune disease which causes pain and inflammation in joints post-playing, but has also made it clear she wants to "achieve other things in life".

Wozniacki has also enrolled at Harvard Business School and says she has a "slam-packed" diary over the next six months.

Her plans include going skiing with her family, a couple of "girls trips" and a belated honeymoon with her husband David, the former NBA basketball star who she married in June last year.

Tears, teddy bears - Melbourne waves goodbye to 'Sweet' Caroline

Wozniacki has long been one of the most respected players in the sport, meaning it was always going to be an emotional farewell whenever she lost at Melbourne Park.

While it was far from a fervent atmosphere during the match - not least because unsurprisingly there were few Danes who had made the 9,900 mile trip at an eye-watering cost - the respectful mood switched to a sentimental celebration after Wozniacki lumped a forehand long on match point.

After embracing with Jabeur at the net, she wandered over to her chair and sat down for a few moments as she contemplated the fact it was all over.

"There are a lot of emotions, a lot of things I can't compartmentalise," a still teary Wozniacki told reporters afterwards.

"A lot of excitement. A little sadness. Flashbacks to since I was a kid to this moment."

Jabeur beautifully paid tribute to the woman whose career she had just ended, saying she was "sad and actually a bit stressed" that she was the one who laid the final blow. Somebody had to.

For Wozniacki fans, the dream farewell might have been in the next round against her great friend, and bridesmaid, Serena Williams.

A shock defeat for the 23-time Grand Slam champion, who also welled up when she was asked about Wozniacki's retirement, meant neither will be returning to Melbourne Park this week.

Wozniacki will not return again, as a player at least, leading to an emotional on-court presentation following Jabeur's brief victory speech.

Australian Open tournament director Craig Tiley appeared with a giant cuddly toy before a tribute from her fellow players, starting with a montage of them saying the word most associated with her career - 'fight', appeared on the big screen.

"Hopefully I will not cry - I brought the tissues just in case," laughed Wozniacki.

Inevitably, the tears did start rolling. Wozniacki's nearest and dearest walked on to share the special moment, dad Piotr - the most influential person in her career having nurtured her talent from precocious age - lifting his screaming daughter into the air before a making a celebratory punch at everything he has seen her achieve.

"I'm not a big crier, but I think when the family came down, I saw my dad pacing himself, that's what he does when he tries not to get emotional," Wozniacki said.

"Then my mum was bawling, she had sunglasses on. My brother was shaking. Looking at David just smiling, crying, being excited.

"That all caught me, I got emotional. I just tried to take it all in."

There was one final tribute. Being serenaded by the entire 10,500 crowd to Neil Diamond's jaunty pop classic 'Sweet Caroline'.

"It's going to be a moment I will never forget."

The occasion was reminiscent of Andy Murray's 'farewell' on the same court 12 months ago - and you know what happened there.

Yet Wozniacki's circumstances are very different to the Briton's and she truly believes this will be a final goodbye.

'She is one of Denmark's all-time sporting greats'

Before leaving court for the final time, Wozniacki ran over to the far baseline to collect a Danish flag - probably the only one in the arena - which had been draped over a safety barrier.

Wozniacki flung it above her shoulders, wafting the flag high in the air in a symbolic gesture marking her place as the small Scandinavian country's only Grand Slam champion.

Watching the moment was former Denmark footballer Thomas Sorensen, who knows Wozniacki and was able to get tickets for him and his family through the player.

"She is a huge sporting personality in Denmark - one of the biggest we have ever had," former goalkeeper Sorensen, who played in the English Premier League before ending his career at Melbourne City, told BBC Sport.

"I've lived here for four years and I've been very fortunate to watch her here - especially in the year she won.

"It is sad but on the other hand it is a celebration. She can be so proud of her career.

"She has been on the top of the game for so many years. Who knows if Denmark as a small country will ever get anyone close to her."

Danish fans watching this special moment in the flesh were few and far between - at least judging by the lack of national colours visible at Melbourne Park.

But wearing her Denmark football shirt paid dividends for 10-year-old Sigred Oestergaard, who was given the final racquet of Wozniacki's career by her husband David.

Originally from the Danish city of Aarhus, she was there with her family after they recently moved to Melbourne.

"It's really, really good," a shy Sigred said of getting the prized momento. "I'm going to put it on the wall."

'I don't know how to say goodbye to you' - players pay tribute

Tunisia's Ons Jabeur: "Congrats on an amazing career. It was an honour to share the court with you today.

"Your fighting spirit has always inspired me and I wish you all the best in this next chapter of your life. You'll be missed but I'm sure we will see you around."

Canada's 2014 Wimbledon finalist Eugenie Bouchard: "Just shed a few tears. Happy retirement!"

Russia's Anastasia Pavlyuchenkova: "Seeing the family of Caroline and her cry made me so emotional uff! Congrats on such a great career and wishing you all the best in your next chapter!"

WTA Insider: "Lots of emotions all around Melbourne Park at the moment. Ash Barty sought out Caroline Wozniacki and her family, giving a hug to each and congratulating them all on a wonderful career.

"Wozniacki sought out Serena in the locker room after loss to comfort her friend."

Tennis Australia chief executive Craig Tiley: "Farewell Caroline always a joy to have you at the Australian Open. All the best with your next moves, we hope to see you again, champion."

Serena Williams says she made "far too many errors to be a professional athlete" as she was knocked out in the Australian Open third round.

The 38-year-old American lost 6-4 6-7 (2-7) 7-5 to China's 27th seed Wang Qiang.

The defeat means Williams' quest for a 24th Grand Slam singles title goes on.

"I can't play like that. I literally can't do that again. That's unprofessional. It's not cool," Williams said.

The seven-time champion in Melbourne beat 28-year-old Wang in just 44 minutes at the US Open in September when the Chinese player won only one game and 15 points.

That was not reflective of the ability of a player who has been a regular fixture in the world's top 30 over the past 18 months and reached a career high of 12 after her run in New York.

This time, after initially flinching when serving for the match at 5-4 in the second set, she made amends in spectacular fashion.

Wang had the tools to hurt Williams and continued to execute them in a third set in which most observers would have backed her illustrious opponent to go on and win.

After briefly faltering again as Williams rallied, Wang sealed victory on her third match point.

"I honestly didn't think I was going to lose that match," said Williams when asked on her thoughts after levelling at one set all.

'I'm going to be training tomorrow' - Williams back to work after shock loss

Williams, seeded eighth, came into the match on the back of winning the Auckland Classic and relatively straightforward wins over Russia's Anastasia Potapova and Slovakia's Tamara Zidansek.

Instead of those results laying the platform for another title challenge, they preceded her earliest exit at the Australian Open since 2006.

"I made a lot of errors. I didn't hit any of those shots in New York or in general in a really long time," Williams said.

"I just made far too many errors to be a professional athlete today.

"I'm definitely going to be training tomorrow. That's first and foremost, to make sure I don't do this again."

Opportunities to equal Margaret Court's record of Grand Slam singles titles are running out for Williams, who is in her 23rd year as a professional.

She has not won a Slam since the 2017 Australian Open, when she was eight weeks pregnant.

Williams says she still has the drive to win that elusive 24th title and believes she can still match Australian Court.

"I definitely do believe or I wouldn't be on tour," she said.

"I don't play just to have fun. To lose is really not fun."

'I trusted myself' - Wang on digging deep to win

Wang grew in confidence after she saved three break points in the sixth game of the opening set. Her firm forehands began to trouble Williams, whose movement could not match her opponent's.

Wang - who defeated current world number one Ashleigh Barty at the US Open before losing to Williams - broke for a 5-4 lead and then served out to seal the first set.

Williams was struggling to gain the upper hand as the unforced errors totted up - they would eventually reach 56 - and she was broken again when Wang converted the second of her three break points with a deep forehand winner.

The Chinese player's form deserted her as she served for the match at 5-4, with Williams breaking back with a superb forehand winner at the end of a 24-shot rally. The American saved two more break points at 5-5 before eventually levelling the match in a one-sided tie-break.

The final set went with serve until the 12th and final game. Wang had wasted two chances to seal victory on Williams' serve before she was presented with another, which was taken when the American netted a backhand.

"After the second set I was a little bit confused, but my mind always said I had to focus on the court, on every point and trust myself," said Wang, who now faces Tunisian Ons Jabeur in the fourth round.

Wang dedicated the victory to her former coach, Peter McNamara, who died from cancer just weeks before last year's US Open.

"I always dream about him," she said. "I think he can see what I play today. He will proud of me. I miss him."

American teenager Coco Gauff stunned defending champion Naomi Osaka in straight sets to reach the fourth round of the Australian Open.

The 15-year-old excelled at the Rod Laver Arena and eased to a 6-3 6-4 victory in 67 minutes

Osaka, the world number four, struggled with unforced errors throughout - making 30 compared to Gauff's 17.

"I don't know where that came from," the American said after the match. "Honestly, like, what is my life?"

"Two years ago I lost in the first round in juniors and now I'm here," Gauff added.

"I was telling myself one point at a time and keep fighting. You never know what happens on this court."

Gauff will play either China's Zhang Shaui or American Sofia Kenin in the fourth round.

It was an uncharacteristically slow start for Japan's Osaka who had won the pair's only previous meeting at last year's US Open.

The 22-year-old could not contain Gauff in the first set, especially when the American was on serve. Gauff completed 81% of her first serves compared to Osaka's 61%.

Despite Gauff making the quicker start, the pair each held serve until the ninth game when the American seized her opportunity.

An easy backhand miss from Osaka gave Gauff break point and it was another backhand error that gave the American the break which she held on to to take the first set 6-3.

The 15-year-old broke the Osaka serve again at the start of the second set, but could not hold for 2-0, allowing the defending champion to break back.

But unforced errors continued to flow from the Japanese player and Gauff broke again to lead 4-3.

She served for the match and Osaka sent three straight returns long before hitting match point into the net, handing Gauff victory in the simplest of fashions.

I don't have the champion mentality yet - Osaka

Osaka is set to drop to ninth in the world after the defeat and could fall out of the top 10, depending on the progress of other players.

Gauff, who becomes the first 15-year-old to reach the last 16 of two Grand Slams since Martina Hingis in 1996, is set to break into the world's top 50 with her first win against a top-five player.

"I don't have the champion mentality yet. That is someone who can win when they are down," Osaka said.

"Sometimes I get overwhelmed and I don't know what to do in these situations.

"I have an age problem - I don't like losing to people younger than me. So I took this very personally."