The Briton had breezed through the first set of the last-16 tie against Slovakia's Viktoria Kuzmova, winning 6-0 in just over 20 minutes.

Raducanu faced far more of a challenge in the second set, and received treatment on her left ankle near the end of it, before pulling out in tears at the start of the third.

"I've put a lot of physical work in the last few months and I've been feeling good and optimistic," she said.

"So to be stopped by a freak injury, rolling an ankle is pretty disappointing, in the first week as well. I thought I was playing some pretty decent tennis.

"The courts are incredibly slick, like very slippery, so to be honest it's not a surprise that this happened to someone ... we'll assess over the next few days and see what the next steps are."

Raducanu had been broken at 2-2 and fell 4-2 behind in the second set, but broke back in the 10th game of the set to level things at 5-5. The Briton was broken again in the very next game, however, before going on to lose the second set 7-5.

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During the match, Raducanu summoned the trainer courtside to heavily strap her left ankle in a long medical timeout.

She attempted to play on but was not able to complete the first game of the third set, acknowledging she could not continue.

Tournament director Nicolas Lamperin responded to Raducanu's claims on Friday by insisting the indoor courts were safe.

He said: "The courts have been checked, the courts are fit to play. We've had a number of matches on these courts and we haven't had any injuries apart from yesterday and the courts had been redone at the start of the year.

"We are obviously very sorry about Emma's injury. Every player works really hard in the off-season and that's not what you expect when you play a tournament in week one.

"However, injuries happen all the time. It could have happened on an outdoor court."

Raducanu was marked as one of tennis' hottest stars when she won the US Open in 2021. Her career since has been dogged by injuries. She retired from matches four times in 2022 and most recently has had to contend with a wrist injury.

Kuzmova will face Montenegro's Danka Kovinic in the quarter-finals, after the latter defeated American Lauren Davis in three sets 4-6 6-3 6-2 to progress.

Cowan: Raducanu injury so unfortunate | 'I'm confident we will see her at the Australian Open'

Former British tennis player Barry Cowan speaking to Sky Sports News on Thursday....

"It's really unfortunate for Emma, and it was one of those freak injuries that can happen to any tennis player.

"Most tennis players, at some stage, have rolled their ankle, but if we go back to how it happened, it was at 5-5 in the second set, and at the time it looked innocuous and more like a slip than a rolled ankle.

"She played for another couple of games, lost the set, then called the medical timeout, had her ankle strapped, and sometimes it can really feel uncomfortable when you have you ankle strapped as heavily as she did.

"Unfortunately for Emma, she was only able to play one point in the third set. So let's wish her well, because the off season by all accounts was very, very positive.

"And when you start a new season it's always with renewed hope. I'm sure she was full of confidence.

"It's still quite a while until the Australian Open, and I would expect her to be fine and to be able to play in Melbourne.

"In her case, she'll find out more tomorrow morning when she wakes up.

"That's been the hardest part of Emma's tennis [lack of meaningful practice]. At times, unfortunately, she has had to pull out, either during a match or before an event.

"You want momentum, you want to be able to build up a head of steam, get some confidence, feel like you get into a flow. But unfortunately for Raducanu, with the injuries she's had, she'll be disappointed she's not able to build on the little bit of momentum she had in December with a good practice schedule with her new coaches.

"Absolutely not [don't write off Raducanu as injury prone]. This can happen to the fittest tennis player, and to the unfittest player. It's a rolled ankle, it's just one of those injuries.

"It's just really unfortunate for Emma this has happened this week. But it has, it's a long year, and I would have thought a scan is the right way to go, because then you know in your mind if everything is fine.

"Sometimes with a sprained ankle you wonder with a little bit of pain: 'I don't want to make it worse', and that's exactly what you don't want to do at the start of a tennis season where she hopes to play 25/30 events.

"In a sport that is brutal, not only in terms of having to beat your opponent over three hours, but mentally and physically, you will have niggles along the way.

"With this particular one, if you are in any doubt at this stage of a season, it's better to make sure you get the right treatment. Because what you don't want is if it is slightly weak and susceptible to worse injury.

"Better to pull out of a match in January and just miss one tournament than miss two or three months. I'm pretty confident we'll be seeing Emma Raducanu a week on Monday at the Australian Open."

Venus Williams blows lead; Zhu Lin, Coco Gauff, Kovinic, Rebeka Masarova through to quarters

Elsewhere, Venus Williams blew a 5-3 last-set lead in a match which stretched over nearly seven hours because of rain in losing to Zhu Lin of China 3-6, 6-2, 7-5.

The 42-year-old Williams fought through every moment of the second-round match which began after noon and ended near 7pm, which began outdoors and ended indoors, and which contained 13 service breaks before finally tipping in favour of Zhu in the last few games.

Seven-time Grand Slam champion Williams, starting her 30th year on the WTA Tour, won her first tour match in nearly two years when she beat Katie Volynets on Monday in the first round of the Auckland tournament. She played only four matches in 2022 and was hoping to progress to the second round of a tournament for the first time since 2019.

Top-seeded American Coco Gauff will face Zhu in the quarter-finals after her 6-4, 6-4 win over compatriot Sofia Kenin, the 2020 Australian Open champion.

Seventh-ranked Gauff also had to play indoors and beat Kenin in just under 90 minutes, levelling their head-to-head record after Kenin beat Gauff en route to the Australian Open title.

Danka Kovinic, the seventh seed, beat former champion Lauren Davis 4-6, 6-3, 6-2 and qualifier Rebeka Masarova beat Anna Blinkova 6-1, 6-4.