Defending champion Sofia Kenin tumbled out out the Australian Open with a stunning second-round defeat to Kaia Kanepi but world No 1 Ashleigh Barty made it safely through.
The American claimed her maiden Grand Slam at last year's event but any hopes of a repeat performance ended in the second round as she was well beaten 6-3 6-2 by the Estonian.
Kenin has been reduced to tears on court on several occasions since she came out of quarantine in Melbourne and admitted she has been struggling to contain her nerves at the prospect of defending the title.
"I felt like I obviously wasn't there. My head wasn't there. Obviously I'm not going to take any credit away from her. She played really well at those good points. I had chances. I just couldn't take it. I obviously know why because the nerves big-time got to me," admitted Kenin.
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"I obviously felt like I'm not there 100 per cent physically, mentally, my game. Everything just feels real off obviously. It's not good."
Kanepi, who reached the final of the Gippsland Trophy warm-up tournament last week, was just the sort of hardened veteran who would look to exploit any mental frailties in her opponent.
"I served really well today, I think this helped a lot," the 35-year-old said. "My game plan was to play aggressive as I usually do."
Next up for Kanepi is a third-round tie against Croatian Donna Vekic, who beat Argentine Nadia Podoroska in her second-round match on Thursday.
Ashleigh Barty came out on top of the all-Australian battle with Daria Gavrilova to make it through to the third round.
Barty looked on course for a comfortable win on the Rod Laver Arena as she was serving for the match at 6-1 5-2 before a Gavrilova comeback saw her take the second set to tiebreak.
Barty, who has had the best part of a year off after opting not to travel during the coronavirus pandemic, survived set points to eventually won 6-1 7-6 (9-7).
The top seed, who was wearing heavy strapping on her left leg, said there are no concerns.
"It's just a little bit of support. I played a lot of matches in the last 10 days after not playing for 12 months, which is natural. It's more of an assistance than anything else," said Barty.
"It's not affecting the way that I can play in any way. It's just more giving the leg some assistance to make sure it doesn't get to a point where it's going to affect me."
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Fifth seed Elina Svitolina ended the hopes of 16-year-old American Coco Gauff.
The Ukrainian, a Wimbledon semi-finalist in 2019, won 6-4 6-3 in an hour and 17 minutes.
Sixth seed Karolina Pliskova, who reached the semi-finals at Melbourne Park two years ago, booked a place in the third round with a 7-5 6-2 victory over American Danielle Collins.
Up next for Pliskova, who is chasing her maiden Grand Slam title, is fellow Czech and 25th seed Karolina Muchova.
The two are friends off the court and practised together during a mandatory two-week quarantine period before the Australian Open.
"Even if we would not practise those two weeks in quarantine, we practice a lot in Czech. We're actually quite good friends," Pliskova said. "Of course, she's a dangerous player. It's going to be very tricky."
Heather Watson, Britain's last remaining hope in the women's singles, fell to defeat against Anett Kontaveit.
The Estonian 21st seed recovered from a shaky start to beat the British No 2 6-7 (5-7) 6-4 6-2 and set up a third-round meeting with American Shelby Rogers.
Switzerland's 11th seed Belinda Bencic needed five match points to put away two-time Grand Slam champion Svetlana Kuznetsova 7-5 2-6 6-4.
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