Australian Open: Angelique Kerber fights back against Hsieh Su-wei to make last eight

Kerber is a two-time Grand Slam champion and former world number one

Former champion Angelique Kerber battled back against world number 88 Hsieh Su-wei to reach the Australian Open quarter-finals.

Kerber, the favourite for the title following her convincing win over Maria Sharapova in round three, recovered from a set down to win 4-6 7-5 6-2.

The 30-year-old German and 21st seed is the last remaining Grand slam champion in the women's singles draw.

She will play American 17th seed Madison Keys in the last eight.

• Live radio & text coverage: Halep & Djokovic

• Federer maintains winning run

• Halep races into quarter-finals

• Edmund says he can win Australian Open

• Live scores, schedule and results

Despite breaking serve in the first game, 2016 champion Kerber struggled in the first half of the match as the unconventional Hsieh, who plays with a double-handed backhand and forehand, hit 20 winners in the first set alone.

Hsieh knocked out third seed Garbine Muguruza and 26th seed Agnieszka Radwanska in previous rounds and looked on course for a first Grand Slam quarter-final until Kerber improved late in the second set.

Kerber served to stay in the match at 5-4 in the second set before winning the next two games to force a decider.

She took the final set in 32 minutes, the quickest of the match, to reach her first Slam quarter-final since winning the US Open in 2016.

"Credit to her, she played an unbelievable match," Kerber said.

"I was running everywhere and she always had the answer. We will see a lot in 2018 from her."

Keys, runner-up in the last Grand Slam of 2017 at the US Open, progressed with a crushing 6-3 6-2 victory over French eighth Caroline Garcia.

The 22-year-old hit 32 winners and nine aces in her 68-minute win.

"It will be another tough match but I will try to continue how I have played in the last week," Kerber said. "I am feeling good."