Ash Barty is Australia's last great hope as she takes on Russian drawcard Maria Sharapova in their Australian Open fourth round clash.

On a bumper Sunday, Roger Federer and Rafael Nadal also face their first serious tests of the tournament.

ROD LAVER ARENA
(8) Petra Kvitova (CZE) def. Amanda Anisimova (USA) 6-2 6-1
(15) Ashleigh Barty (AUS) def. (30) Maria Sharapova (RUS) 4-6 6-1 6-4
(2) Rafael Nadal (ESP) def. Tomas Berdych (CZE) 6-0 6-1 7-6

(3) Roger Federer (SUI) vs Stefanos Tsitsipas (GRE)

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(5) Sloane Stephens (USA) vs Anastasia Pavlyuchenkova (CZE)

MARGARET COURT ARENA
Danielle Collins (USA) def. (2) Angelique Kerber (GER) 6-0 6-2

(6) Marin Cilic (CRO) vs (22) Roberto Bautista Agut (ESP)

MELBOURNE ARENA
Frances Tiafoe (USA) def. (20) Grigor Dimitrov (BUL) 7-5 7-6 6-7 7-5

Red-hot American through to quarters on his birthday

American giant killer Frances Tiafoe is through to his first grand slam quarter final after he ambushed No. 20 seed Grigor Dimitrov 7-5 7-6 6-7 7-5.

Tiafoe, who bounced out No. 5 seed Kevin Anderson earlier in the tournament, proved too hot to handle for Dimitrov, who blew his golden opportunity in the second set.

The Bulgarian star found himself two sets down after he butchered three set points when ahead 6-3 in the second set breaker.

Tiafoe then jagged five straight points to take the tiebreak 8-6. His momentum continued in the third set where he secured an early break of serve, but was eventually run down late in the set as Dimitrov sent it to a fourth set.

In a tight fourth set, Tiafoe picked his moment to strike and secured a crucial break of serve to go ahead 6-5.

He went on to serve out the match in just over 3.5 hours.

Bizarrely, the scoreboard showed Dimitrov actually won more points for the match, but couldn't match Tiafoe in the big moments when it mattered the most.

"I told my parents ten years ago that I was gonna do this, I was gonna change their lives and my life. Now I'm in the quarters of a slam at 21 ... I can't believe it, man," he said.

Nadal survives brief scare after brutal carnage

Rafael Nadal has survived a brief scare against former top ten player Tomas Berdych to book a quarter final with American Frances Fiafoe.

Nadal was unstoppable in the first two sets, ripping Berdych's game to pieces on his way to a 6-0 6-1 lead in less than an hour. The Spaniard also peeled off the first nine service games to all-but break Berdych's spirit.

However, Berdych got back to his feet in the third set and forced a tiebreaker.

Nadal found another gear in the breaker as Berdych instead lost his cool over the malfunctioning service clock time keeper on court.

Nadal eventually took the tiebreak 7-4 to move through in straight sets 6-0 6-1 7-6.

'Holy s***': World No. 2 pulverised

American star Danielle Collins has produced one of the biggest shocks of the Open, brutalising No. 2 seed Angelique Kerber in a 6-0 first set demolition.

The thumping continued in the second set where Collins again proved unstoppable on her way to a 6-0 6-2 win, which wrapped up her spot in the quarter-finals in just 56 minutes on court.

Collins stunned the former Aussie Open champion to take the first set in just 20 minutes. She dropped just nine points in the entire set.

Collins had previously never won a grand slam match before the 2019 Australian Open, but she was showing no sign of her No. 380 ranking when she stepped onto Margaret Court Arena to face the German champion.

A controversial bathroom break taken by Kerber at the end of the first set appeared to slow down the American's momentum. Kerber finally woke up in the second set to have the set on serve at 2-2.

However, Collins found another gear and peeled off the last four games to seal her spot in the last eight.

She will play the winner of Sloane Stephens and Anastasia Pavlyuchenkova in the quarter-finals.

Sharapova booed after 'pathetic' act

Ash Barty has ended Australia's 10-year wait for a women's quarter-finalist at the Aussie Open with an emphatic, dramatic comeback win over champion Maria Sharapova.

Australian Ashleigh Barty beat Maria Sharapova to move into the quarter-finals of the Australian Open. Photo / Getty Images
Australian Ashleigh Barty beat Maria Sharapova to move into the quarter-finals of the Australian Open. Photo / Getty Images

The Melbourne crowd turned on Maria Sharapova at the Australian Open after the Russian disappeared for a seven minute bathroom break as Barty charged to the second set.

Barty caught fire from 1-1 in the second set where she peeled off nine straight games and broke Sharapova's serve four-times consecutively to eventually run away to a convincing 4-6 6-1 6-4 victory that puts her through to a quarter-final against No. 8 seed Petra Kvitova on Tuesday.

Barty is the first Australian woman to make the final eight at Melbourne Park since Jelena Dokic's fairytale run in 2009.

Sharapova made a fightback of her own late in the third set and forced Barty to serve out the result after an enthralling, see-sawing third set which saw Barty begin to tighten up as she neared the finish line.

She eventually kicked back into gear as all champions do to wrap up the biggest win of her career in just under 2.5 hours.

The match wasn't without its controversy β€” Sharapova was loudly booed by the Melbourne crowd when returning for the start of the third set following a lengthy bathroom break.

The Aussie tied the match up 4-6 6-1 when she broke serve in consecutive service games, seizing momentum as the pair headed into the decisive third set.

However, Sharapova used her guile to try to stem the flow by taking a bathroom break that extended beyond seven minutes.

The controversial tactic clearly upset the heavily pro-Barty crowd and they let Sharapova know about when she returned to court.

Some Aussie tennis commentators even labelled Sharapova's tactic "pathetic".

Barty was also playing some mindgames, waiting out on court for the moment that Sharapova finally returned to Rod Laver Arena.

Channel 9 commentator Sam Smith described the use of toilet breaks as the one area left on the WTA Tour that is yet to be "cleaned up".

It clearly didn't help Sharapova. Barty secured her third straight break of serve when play resumed to take a 2-0 lead in the third set.

Barty's fourth straight break of serve then made it eight consecutive games for Barty as she took a 3-0 lead in the decider.

It was only with Barty ahead 4-0 that Sharapova finally held her serve to stem the bleeding.

Sharapova then sent a scare through Australian tennis when she got one break of service back and drew back to within one game of Barty at 4-3 in the third set.

With the finish line in sight Barty tightened up and it was a recipe for some of the craziest tennis the tournament has seen so far.

At deuce in Sharapova's service game the pair played out one of the points of the tournament which ended after 16 shots, including an around the net retrieval from Sharapova.

Barty also had to defend two break points on her next service game to go ahead 5-3 after 15 minutes of extreme drama.

She then had to keep her nerve and serve out the most memorable win of her career.

Sharapova's cold Barty rejection

Maria Sharapova was all business when she walked out onto Rod Laver Arena without acknowledging Aussie star Ash Barty before their blockbuster fourth round match.

Maria Sharapova in action at the Australian Open. Photo / Getty Images
Maria Sharapova in action at the Australian Open. Photo / Getty Images

Sharapova walked out second and had to follow a thunderous roar given by the Aussie crowd when Barty made her first appearance on court. The No. 30 seed walked past the Aussie to her seat without even a look in Barty's direction.

It comes after both players shared an awkward warm-up earlier on Sunday when they were both forced to share Rod Laver Arena just hours before their showdown.

The pair were spotted by TV cameras going through their paces and hitting with their practice partners just metres away from each other.

American darling's dose of reality

Amanda Anisimova delighted American audiences with her run to the fourth round β€” but didn't last long today.

Anisimova, 17, was smacked 6-2 6-1 by eighth seed Petra Kvitova, who was incredibly dominant on serve.

Kvitova has bullied her way past the teen sensation to become the first woman through to the quarterfinals. She progresses to play the winner of Ash Barty's blockbuster against Maria Sharapova.

Anisimova, the youngest woman since 2007 to reach the last 16 in Melbourne, was broken five times and failed to secure a break point opportunity.

Novak slams damaging player leaks

World number one Novak Djokovic has hit back at claims he is trying to oust ATP Tour chief Chris Kermode.

A battle for control of the men's tour has been waged all-week at Melbourne Park, with Djokovic, who heads the player council, pitted against several big name stars including Rafael Nadal and Stan Wawrinka who have argued for Kermode's retention.

After Nadal revealed his opinion had not been sought over whether Kermode would survive when his contract expires later this year, Wawrinka penned a strongly-worded letter on the issue.

Djokovic called for calm after his third round win on Saturday and denied he was forcing Kermode out.

"I don't know why people keep on talking about me as being against Chris. Who said that that was the truth?" Djokovic said.

"One of my greatest concerns right now, of every council member, is that we have leaking information from someone within the council in the last couple months.

"Many of those things that have been leaked to certain media are also not 100 per cent true. It's obvious that there is a certain kind of one-dimensional agenda in place. Players and certain media are served with quite a one-sided story ...

"I saw Stan's statement, as well. I respect him. We have a great friendly relationship. I respect his opinion, anybody else's opinion ... But at the same time I encourage them and anybody else who has an interest to approach me, approach all the council members if they need more information, as we will do the same to them in the next period. But where is the rush?"