Teenager Madison Keys shocks Wimbledon champion Petra Kvitova at Australian Open
Unseeded American, a big-serving baseliner, powers past No 4 seed to reach the last 16
Czech fourth seed Petra Kvitova crashed out of the Australian Open on Saturday, falling in straight sets to unseeded American teenager Madison Keys, who is coached by former great Lindsay Davenport.
World No 35 Keys, 19, beat the reigning Wimbledon champion 6-4, 7-5 in the third round, setting up an all-American last-16 clash with Madison Brengle.
My hands are still shaking. Right now I can't even process this, I'm just so excited
"My hands are still shaking. Right now I can't even process this, I'm just so excited," she said, paying tribute to the "amazing" Davenport, a three-time grand slam champion who won in Australia in 2000.
Like Davenport, Keys is a big-serving baseliner with powerful ground strokes, which she used to full effect against Kvitova, who has admitted to struggling with nerves in the tournament.
The Czech, a semi-finalist at Melbourne Park in 2012 but loser in the first round last year, let Keys dictate terms in a performance that included six double faults and 32 unforced errors.
Fired-up men's top seed Novak Djokovic powered into the fourth round, joining sizzling fellow world number one Serena Williams.
The Serb, whose chances of a fifth Australian crown have vastly improved after Roger Federer's shock exit on Friday, ground down Spaniard Fernando Verdasco 7-6 (10-8), 6-3, 6-4.
He said he was highly motivated and over the virus that hampered his lead-up to the season's opening grand slam.
"He [Verdasco] was a former top-10 player. Somebody that loves playing on the big stage, a powerful game. I'm glad to go through in straight sets," he said.
Williams, vying for a sixth Australian title and the first since 2010, was slow to find her groove against 26th-ranked Ukrainian Elina Svitolina, going down 6-4 in the first set.
But she rebounded strongly under the blazing sun on Rod Laver Arena to rattle through the next two sets 6-2, 6-0.
"When in doubt just start running as fast as you can, that's what Venus always told me, that helped," said Williams, whose world number one ranking is on the line if she fails to win the title.
She added that her elder sister's late-career renaissance was an inspiration.
"She's winning, she's doing so well and I can do better. We always motivate each other. I'm so proud of her and we're so excited."
Venus rallied from behind to defeat Camila Giorgi of Italy 4-6, 7-6 (7-3), 6-1 to make the second week of a grand slam for the first time since Wimbledon 2011.
Victoria Azarenka, the champion in 2012 and 2013 who is unseeded this year after an injury-marred 2014, also kept going, continuing her comeback by downing Czech 25th seed Barbora Zahlavova Strycova.
Defending men's champion Stan Wawrinka, who beat Rafael Nadal in the final last year, could meet Djokovic in the semi-finals and stayed on track with a 6-4, 6-2, 6-4 victory over Finland's Jarkko Nieminen.
The Swiss was pleased with his progress.
"It's been three really good matches, I think my game is there and I'm really happy to get through again," said Wawrinka, who will now meet Spain's Guillermo Garcia-Lopez.
Eighth seed Canadian Milos Raonic and Japan's fifth seed Kei Nishikori also went through.
