Germany's Angelique Kerber lets off some steam during her third-round victory over Czech Kristyna Pliskova at the Australian Open on Friday. World No 1 Kerber advanced 6-0, 6-4 to set up a last-16 meeting with American Coco Vandeweghe. Jason Reed / Reuters

World No 1 Angelique Kerber said she is fired up for a last-16 clash with Coco Vandeweghe after blowing away Kristyna Pliskova at the Australian Open on Friday.

Defending champion Kerber, who was taken to three sets in her opening two rounds, smashed hapless Czech Pliskova 6-0, 6-4 on Rod Laver Arena as she finally got into her stride.

She now faces the racquet-smashing Vandeweghe, who ended the campaign of Canadian comeback queen Eugenie Bouchard 6-4, 3-6, 7-5.

"It was not so easy today, she is a tough opponent who serves well and hits the ball strongly. I tried to stay focused until the last point," said Kerber.

She watched some of the Vandeweghe-Bouchard match, which preceded hers, and said she would be ready for the American on Sunday.

"I think it will be a little bit similar to today, but, of course, Coco is a tough opponent. She played good today," said Kerber.

"I know that she's serving good, too. I have to move good, be ready, bring a lot of balls back, but also be aggressive as well, like I can play."

Bidding to become the first woman to successfully defend an Australian title since Victoria Azarenka in 2013, Kerber had a tough time in her opening two rounds.

The German also had an indifferent build-up to Melbourne with early exits in Brisbane and Sydney.

However, she is starting to find her groove with the quarterfinals in sight.

"I'm ready for every single match every single day. This is what counts, because I know that this is the only way to play good tennis, especially (over) two weeks," she said.

The 35th-ranked Vandeweghe threw a temper tantrum in her second-round win over Pauline Parmentier, slamming her racquet into the ground three times when she gave away a break point.

But the fiercely competitive 25-year-old largely kept her emotions in check against Bouchard, only throwing down her racquet once, but not smashing it.

Despite having to slog through three sets against the 22-year-old Canadian - battling back after her career plunged into a tailspin-Vandeweghe said she always expected to win.

"It was kind of expected, in my mind, to get the win and to move a step closer to achieving what I want to achieve for this year and also this tournament," she said.

Coco coaxed to answer call of duty

Coco Vandeweghe was in two minds whether to answer the call when an unknown number with a strange international dialling code popped up on her phone last year.

Luckily, she said, she answered it rather than do what she normally does and divert it to voicemail.

Turns out the call was from former world No 1 Martina Hingis. The Swiss wanted to know if she would play doubles with her at the tail end of 2016, including at the US Open.

"I was thinking 'who the heck is calling from this foreign number?', and I usually don't answer my phone," the 25-year-old said courtside after beating Eugenie Bouchard 6-4, 3-6, 7-5 to advance to the fourth round.

"I could have sent Martina straight to my voicemail and that would have been the highlight of my career."

As it transpired Vandeweghe went even further - she turned down Hingis, who has won five Grand Slam singles titles and 12 doubles crowns.

Vandeweghe had committed to playing both the Cincinnati and US Open tournaments with other partners and did not want to let them down.

So the answer was thanks, but no thanks.

Until, that is, the 25-year-old American had a conversation with coach Craig Kardon.

"I told my coach, 'Hey Craig, guess what? Martina just called me'. And he was like, 'which Martina?', because he used to coach Navratilova. And I said, 'no, Hingis, Hingis called me,'" Vandeweghe added.

"I told him that she asked me to play doubles and I told her 'no'. He said, 'What? Are you kidding?'."

Vandeweghe did not require much more convincing and canceled on the other two players she had committed to.

She and Hingis went on to make the final in Cincinnati and the semifinals at Flushing Meadows.