World number one Ashleigh Barty overcame a big hurdle on her path towards what she hopes will be a first Australian Open title.

The home favourite took on young American Amanda Anisimova, who had stunned defending champion Naomi Osaka in the third round, and booked her spot in the quarter-finals with a 6-4 6-3 victory.

Barty did see her run of 63 consecutive service holds come to an end when she was broken early in the second set but she won six of the next seven games.

Anisimova enjoyed feeding off the power of Osaka but Barty did not give her the same rhythm, using her backhand slice intelligently and consistently putting the ball into the corners as she made it through to the quarter-finals for a fourth consecutive year.

In the last eight, Barty will take on American Jessica Pegula, who reached the quarter-finals for the second year in a row with a 7-6 (0) 6-3 upset of fifth seed Maria Sakkari.

Madison Keys beat eighth seed Paula Badosa in straight sets

The other match in the top half will pit fourth seed Barbora Krejcikova against a resurgent Madison Keys.

The American had long been tipped as a potential grand slam champion and made the final of the US Open in 2017 but this is her first grand slam quarter-final since the French Open almost three years ago.

Keys began the season with a title in Adelaide and crushed eighth seed Paula Badosa 6-3 6-1 at Melbourne Park.

"I think it's obviously easy to say it now, that as long as you keep doing the right things, things will work out and all of that," said Keys.

"I felt like I was doing a lot of the right things last year, I was doing my best, and it just wasn’t happening. Tennis can change in a week. Just knowing that it will eventually get better, you just kind of have to hold onto that."

Keys missed this tournament last year after testing positive for Covid-19 and she admitted she has struggled with the restrictions imposed on players.

"Not being able to get out, go for walks, separate myself from the tournament a little bit, got really difficult," she said.

"Then it kind of spiralled from there. It just felt like it was just another brick on top of another brick. Everything got a little bit heavier and heavier and harder to deal with."

Badosa also won a tournament to begin the season but was blown away by the power of Keys.

The Spaniard said: "Sometimes I was serving 180 [kph]. I had to look what the serve said because I didn't understand how a winner came back that fast. I thought I was serving bad. Then I saw it was her game, that she was playing very, very good."

Krejcikova has taken becoming an unexpected grand slam champion completely in her stride since lifting the title at Roland Garros last spring and she eased to a 6-2 6-2 victory over two-time former champion Victoria Azarenka.