MELBOURNE (AFP) - Angelique Kerber kept her hopes of a second Australian Open title alive with a battling come-from-behind 4-6, 7-5, 6-2 victory against Taiwan's tenacious Hsieh Su-wei in the fourth round on Monday.

The German was run ragged in the first two sets by unseeded Hsieh, a former doubles world number one, as she negated the pace of her power game with a delightful mixture of drop shots, lobs and finessed groundstrokes.

"First of all, credit to her," said Kerber, the 21st seed who won the Melbourne title in 2016. "She played an unbelievable match. She was hitting the balls very well."

In the early stages Kerber was unable handle the variety of world number 88 Hsieh who was bidding to reach her first Grand Slam singles quarter-final.

The Taiwanese was looking for a third big-name scalp in a row knocking out Wimbledon champion Garbine Muguruza in round two and then former world number two Agnieszka Radwanska.

"I was feeling like I was running everywhere. Inside the court and outside I was everywhere," Kerber said. "She was playing a lot of corners and drop shots. I was just trying to run behind the ball and bounce them back."

Kerber dropped the first set and was clinging on towards the end of the second, serving to save the match at 4-5.

After levelling at 5-5 the former world number one blasted out a scream as she finally got the decisive break to go 6-5 up before holding to love to take it to a decider.

It knocked the wind out of Hsieh's sails and she immediately surrendered a break at the start of the third.

When a second soon followed the end came after two hours and eight minutes of sheer entertainment.

"Very well done how she played," said Kerber. "And also in her the last three (matches). We will see a lot in 2018 from her."

Kerber will play Madison Keys for a place in the semi-finals after the American 17th seed steamrollered French eighth seed Caroline Garcia 6-3, 6-2.