An inconsistent performance from Karolina Pliskova nearly resulted in an exit from the Australian Open, a fate Caroline Wozniacki was unable to avoid.
World number five and last year's US Open finalist Pliskova did not drop a game in the second set against Jelena Ostapenko, but had to rally back from 5-2 down in the decider to win 4-6 6-0 10-8.
Wozniacki had eased through her opening two matches but was unable to maintain that form against Johanna Konta, the 2016 semi-finalist triumphing 6-3 6-1.
Serena Williams made light work of Nicole Gibbs by beating her 6-1 6-3, while Ekaterina Makarova ended the campaign of reigning WTA Finals champion Dominika Cibulkova 6-2 6-7 (3-7) 6-3.
There were also wins for Barbora Strycova, Daria Gavrilova, Jennifer Brady and Mirjana Lucic-Baroni.
PLISKOVA PUSHED TO THE LIMIT
Pliskova lost a combined four games across her opening two matches in Melbourne, but it was a very different story against Ostapenko.
The Czech failed to convert match point in game 12 of the third, eventually seeing out the win after two hours and five minutes - Ostapenko's 43 unforced errors contributing to her downfall.
Pliskova said: "I think I was a little bt lucky in the end, she was playing really well today and she was maybe the better one.
"When she was 5-2 up in the third set she was missing a little bit more, so I was just staying in the game and still fighting and also deserved to win."
ICE SKATING THE SECRET TO SERENA'S CELEBRATION
Williams celebrated her routine victory over Gibbs with an on-court spin, and she revealed the inspiration behind it.
She told a media conference: "I can't do a triple Lutz, but I can maybe do a double. I have no idea. I just close my eyes, and I just spin and I pray I don't fall. If I do, I get up.
"I used to ice-skate when I was younger, but I was never a figure skater. Obviously I watched the Winter Olympics, and the figure skating was the only thing I wanted to see."
WOZNIACKI TIPS KONTA TILT
Konta produced her best display at a major at this event last year, and Wozniacki was so impressed following their match she backed the ninth seed to put up a good fight against Williams should they meet in the quarter-finals.
Wozniacki said: "I think if she keeps playing like this, then she has good chances against Serena. Obviously Serena is a champion, has won so many grand slams. She's been in tough positions. But I think Johanna is playing on a very high level right now."
Konta will have to overcome Makarova before contemplating a meeting with the world number two.
Jo Konta blasts her way into the 2nd week, beats Caroline Wozniacki 63 61.-- WTA Insider (@WTA_insider) January 21, 2017
Konta: 31W/23UFE, 0 BPs.
Wozniacki: 6W/14UFE, 37% 2nd serve won.
AGE NO OBSTACLE FOR LUCIC-BARONI
Maria Sakkari was just 16 months old when Lucic-Baroni began her professional tennis career.
But it was the 34-year-old who triumphed in a third-round clash with the young Greek, battling from a set down to win 3-6 6-2 6-3.