Simona Halep admits ankle pain meant sleepless night before latest Australian Open victory

World No. 1 Simona Halep has yet to win a major, but she has shown the heart of a champion here, fighting her way through to the quarter-finals despite a badly injured ankle.

Halep rolled the ankle in her opening match against Destanee Aiava, but still survived a record-equalling 3hr 44min shoot-out with Lauren Davis in the third round. As she admitted on Monday, she was unable to sleep on Saturday night because of the pain.

Halep has the tenacity of a detective or an investigative reporter, and she has refused to let this tournament go. Drawn against Naomi Osaka on Monday – an opponent no-one enjoys playing because of her heavy and unpredictable strokes – she handed out a 6-3, 6-2 thrashing, thus reminding the rest of the field that she is still in the mix.

“Last night was really tough,” said Halep. “I couldn't sleep. I had pain everywhere. But I slept before the match two hours, and I was fresh after that. I felt good. Ankle is still sore. But I'm not thinking about that any more. I saw that I can win matches with it, so now I'm not that worried any more.”

Halep will have to deal with her injury after the tournament, but this is not a new situation for her. As she admitted after the Aiava match, she has suffered these sorts of ankle rolls at least five times. As a result, the ligaments have lost their tautness, and she is vulnerable to repeat incidents.

Here, though, she was bullish enough to admit that she had set out “to break her [Osaka] a little bit physically and also mentally”. Halep’s plan came off, as she won six of the last seven games to earn a quarter-final meeting with Karolina Pliskova.

Earlier in the day, the 2016 Australian Open champion Angelique Kerber – who is the last former major-winner left in the draw – survived the sternest of tests against the deft and wily Su-Wei Hsieh of Chinese Taipei.

Hsieh - whose best win until this tournament had come against Johanna Konta at Roland Garros last year - has a deceptive double-handed style that recalls the French magician Fabrice Santoro. She probably hits the ball at half the speed of a power player like Madison Keys – who  hammered eighth seed Caroline Garcia by a 6-3, 6-2 scoreline on Monday. But she doesn’t half put it in some awkward positions, and the only thing that saved Kerber was her desperate retrieval skills.

“I think that was the key at the end, that I really could run forever,” said Kerber, who must have the strongest legs on the tour. “I was feeling that I was running from the first point until the last point. A lot of metres, actually.”

Kerber and Keys will now collide on Wednesday in a heavyweight quarter-final. As for Pliskova, she overcame Barbora Strycova last night in the battle of the Czechs.