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.