Kvitova reaches quarters, Kerber and Sharapova out

Two-time Wimbledon champion Petra Kvitova blazed her way into the Australian Open quarterfinals on Sunday with an emphatic straight sets win over American teenager Amanda Anisimova.

The Czech eighth seed downed the unseeded 17-year-old 6-2, 6-1 to set up a last eight meeting with 15th seeded Australian Ashleigh Barty.

Kvitova is on a nine-match win streak this year after claiming the Sydney International warm-up title and is yet to drop a set in four matches at the season-opening Grand Slam.

But the 28-year-old said she was wary of Anisimova, who defeated her last year in Indian Wells.

"It's always difficult when you play someone who's beaten you before," she said.

"I started very well and when the nerves went away I was much better."

Kvitova's best result at Melbourne Park was a semifinal appearance in 2012 and this year's advance to the last eight is her most successful run since a burglar slashed her left hand with a knife in December 2016.

The attack, which happened at her home in the Czech Republic, left injuries which required extensive surgery and forced her out of the game for six months.

Kvitova said she was enjoying her red-hot run of form.

"I'm feeling good. I'm really enjoying my time on the court and playing tennis, which is the main thing for me," she said.

Anisimova, who shares an agent with her childhood idol Sharapova, made a nervous start, committing three unforced errors in the opening game to go down a break.

The teenager, the youngest player to reach the fourth round at Melbourne Park since 2006, regathered as the Czech went hunting for another break.

She double faulted and was caught off guard with a drop shot but stubbornly defended her serve in a game that went to deuce seven times.

Kvitova was relentless though, picking off the youngster's second serve to snatch a second break then claiming the first set after 32 minutes.

She never looked back, racing home in the second after claiming six straight games.

PAVLYUCHENKOVA KNOCKS OUT FIFTH SEED STEPHENS

Unseeded Russian Anastasia Pavlyuchenkova ground down American fifth seed Sloane Stephens to reach the quarterfinals in a late-night epic that ended in the early hours of Monday.

The world number 44 beat Stephens 6-7 (3/7), 6-3, 6-3 to set up a last eight clash with another American, Danielle Collins who knocked second seed Angelique Kerber.

"I really appreciated that some of you guys stayed," said the Russian, who also make the quarterfinals in 2017.

"I heard someone was yawning during the match though, so I'm sorry. I thought it was quite an exciting match, but anyway I'm happy I stayed awake."

Former US Open champion Stephens took an early break in a match that began at 11:23 pm Sunday due to yet another scheduling logjam at the season-opening Grand Slam.

But she blew a 4-1 first set lead as Pavlyuchenkova broke back and forced a tie-break, which the American won 7-3 to take the first set after 61 minutes.

She gained an edge again to open the second, only to give away a double break, allowing the Russian to serve it out after 43 minutes.

The first game of the decider was a 17-minute arm wrestle that went to deuce 10 times as Stephens fended off eight break points, prompting cries of "hurry up" from the few remaining spectators.

Stephens's mistake rate climbed as the match wore on and Pavlyuchenkova finally secured the win at 1:53 am.

This year's tournament featured the latest ever women's match when Spain's Garbine Muguruza defeated Briton Johanna Konta in a second-round clash that began at 12:30 and ended at 3:12 am.

Konta later slammed the scheduling as "dangerous" and unhealthy.

KERBER STUNNED BY DEBUTANT

World No 2 Angelique Kerber was dumped from the Australian Open by unseeded American Danielle Collins in the biggest upset yet at this year's season-opening Grand Slam.

Collins, making her debut in the tournament main draw, humiliated the German three-time major champion 6-0, 6-2 to set up a quarterfinal clash with either fifth seeded fellow American Sloane Stephens or Russia's Anastasia Pavlyuchenkova.

BARTY STUNS SHARAPOVA

Ashleigh Barty stunned five-time Grand Slam winner Maria Sharapova in a three-set thriller to reach the quarterfinals.

Roared on by a packed Melbourne Park crowd, the 15th seed defeated the Russian 4-6, 6-1, 6-4 to become the first Australian to make the last eight of the tournament in a decade.

After losing a tight first set, Barty went on a nine-game winning streak to take the second before holding off a Sharapova fightback late in the third.

"That was a little bit close, wasn't it?" the 22-year-old said after sealing the win with an ace.

"I gave myself opportunities in the third set and couldn't take them. I had to take a deep breath and trust the work that I've done with my team. Go up and hit my spots."

Her next opponent is Petra Kvitova, who is on a nine-match winning streak including defeating the Australian in a tight three-setter to decide the final of the Sydney International warm up.

Barty praised the fighting qualities of Sharapova, who appeared to have wilted in the Australian sun before giving her opponent some nervous moments late in the match.

"She is an absolute champion," Barty said of the 31-year-old, who dumped defending champion Caroline Wozniacki from the tournament in the previous round.

"She was never going to go away. I knew I had to keep chipping away."

Sharapova, seeded 30th this year as she tries to rejoin the game's elite after returning from a 15-month doping ban in 2017, struggled with her serve for much of the match.

She committed 10 double faults and made 51 unforced errors.

Barty lost her only previous meeting with Sharapova in Rome last year but has won seven of her eight matches in 2019.