World number one Halep has endured a gruelling tournament in Melbourne as she attempts to break her grand slam duck, but the Romanian needed just under one hour and 20 minutes to put Naomi Osaka to the sword in round four.

The fact that Halep is still in the tournament is testament to her fortitude. In round one, she overcame an ankle injury and a 5-2 first-set deficit to defeat Destanee Aiava, before in the last 32 she survived three match points to win a deciding set 15-13 against Lauren Davis.

On this occasion, it was a more straight-forward 6-3 6-2 win over Osaka that punched her ticket into the last eight for the first time since 2015.

"I didn't expect to reach the quarter-finals. I didn't expect also to stop the tournament, even if I was injured. I had nothing clear in my head. I just went on court, [and] take it match by match," Halep said of her progress.

A resurgent Kerber has played her way into contention for a second Australian Open title, but had to negotiate her way past a tricky Hsieh on Rod Laver Arena.

Hsieh has earned plenty of plaudits throughout the tournament, though, and proved a tricky customer for the German before succumbing to a 4-6 7-5 6-2 defeat.

Kerber, who outclassed Maria Sharapova in the previous round, said of her win: "I was everywhere today, inside and outside of the court, she made me run everywhere. She played a lot of shots into the corners, made a lot of drop shots, so I was trying to simply bring it back."