- Third seed Serena Williams wins despite hitting herself in the face with her racket
- Defending champion Victoria Azarenka also into Australian Open third round
- World No. 2 Roger Federer and third seed Andy Murray ease to wins
- Rafael Nadal to make his return to action at tournament in Chile next month
Serena Williams once again battled through the pain barrier to advance at the Australian Open on Thursday, but this time the American third seed's injury was entirely self-inflicted.
After rolling an ankle during her first round win the 15-time grand slam champion hit herself in the face with her racket as she brushed aside Spanish teenager Garbine Muguruza 6-2 6-0.
It left her anxiously checking her mouth for damage.
"I think it happens to everyone, but I have never busted it wide open like that," the five-time Melbourne winner told reporters after setting up a third-round meeting with Japan's Ayumi Morita.
"So, yeah, I was like, 'Oh, no. I can't have a tooth fall out.' That would be horrible."
Williams allayed any fears her ankle would hinder her progress at the tournament, saying she felt no discomfort -- although she did take painkillers.
"I didn't feel anything today," the 31-year-old added. "Obviously when you go out to play you're heavy on adrenaline and you're really pumped up.
"Usually I feel injuries after the match, but so far, so good. I felt pretty, much better than I ever dreamed of expecting to feel.
"I feel everybody in the tournament probably is on some sort of pain relief ... I don't do injections. Just tablets."
Williams remains on course for a semifinal showdown with world No. 1 Victoria Azarenka after the Belorussian took just 55 minutes to beat Greece's Eleni Daniilidou 6-1 6-0.
If the top seed seemed like she was a woman in a hurry, it was because she was trying to avoid getting sunburned in the scorching Australian heat.
"I was trying to play fast," said the 23-year-old, who will play American Jamie Hampton in the third round. "The first match I got a little bit sunburned. You don't want to make that mistake again.
"I was prepared for it, you know. I think everybody knew few days before that that it's going to be really hot. Even at 11 a.m. you could really feel it. I wasn't sure if we were playing with closed roof or open roof.
"Right before the match I saw it was closed. I thought, 'Wow, good.' It wouldn't be so hot. It wasn't a problem."
Eighth seed Petra Kvitova was stunned by world No. 53 Laura Robson, going down 2-6 6-3 11-9 in a match which lasted three hours at finished at 00:30 local time.
Britain's Robson recovered from 0-3 down in the final set to reach the third round of the event for the first time, and she will next meet American 29th seed Sloane Stephens.
Former world No. 1 Caroline Wozniacki continued her bid for a maiden grand slam title with a 6-1 6-4 defeat of Croatia's Donna Vekic. The Danish 10th seed's next opponent will be unseeded Ukrainian Lesia Tsurenko.
Roberta Vinci has never been beyond the third round in Melbourne but the No. 16 from Italy will have a chance to address that against Russia's Elena Vesnina after recording a 6-3 6-2 victory over Akgul Amanmuradova of Uzbekistan.
In the men's draw, second seed Roger Federer and world No. 3 Andy Murray both continued their strong starts to the tournament with emphatic victories.
Switzerland's Federer, looking for an Open era-record fifth Melbourne triumph, was rarely troubled as he beat experienced Russian Nikolay Davydenko 6-3 6-4 6-4.
Next up for the 17-time grand slam winner is Australian rising star Bernard Tomic, who Federer beat in the fourth round of last year's tournament.
"I think there's always excitement about Aussies playing here," Federer, 31, told reporters. "I played him here last year. The crowd was great. I played him in Davis Cup. Crowds were fair there, too. I expect something similar.
"Hopefully we're going to live up to the expectations and live up to the match. Hopefully it's not going to be a bad match. I don't want that to happen."
Murray was beaten by Federer in the 2010 final, but having clinched his first grand slam title at last year's U.S. Open the Briton will be hoping to win in Melbourne having twice been a runner-up.
He set up a third round encounter with Lithuania's Ricardas Berankis after a comfortable 6-2 6-2 6-4 win against Portugal's Joao Sousa.
Sixth seed Juan Martin del Potro eased past German Benjamin Becker 6-2 6-4 6-2, while French seventh seed Jo-Wilfried Tsonga battled to a straight-sets win over Japan's Go Soeda.
Meanwhile, former world No. 1 Rafael Nadal will make his long-awaited return to action at the Chile Open in Vina del Mar early next month.
Spain's 11-time grand slam winner has not played since injuring his knee at Wimbledon last June, and had to delay his planned comeback in Melbourne after suffering an illness in December.
Nadal will also play in another South American clay-court tournament, the Brazil Open starting on February 11, as he seeks to regain fitness ahead of his French Open title defense.