Andy Murray has won 10 matches in a row Serena Williams and Victoria Azarenka came through their first uncomfortable moments and Andy Murray was also tested before reaching the Australian Open's last 16 on Saturday .
Williams, eyeing a calendar-year Grand Slam, was broken for the first time in the tournament by Japanese number one Ayumi Morita, before recovering from 0-3 down in the second set to win 6-1, 6-3.
Defending champion Azarenka screamed at herself and thrashed her racquet before overcoming an unexpectedly stiff challenge by America's Jamie Hampton, who bravely played through severe back pain.
Argentina's Juan Martin Del Potro, seeded six, became the tournament's biggest casualty when the 2009 US Open champion slumped to a five-set defeat to unseeded Frenchman Jeremy Chardy.
Jo-Wilfried Tsonga and Richard Gasquet also went through, and with Gilles Simon playing Gael Monfils later France was assured of having four men in the fourth round, equalling their best performance at the tournament.
In the most competitive day so far, Murray extended his Grand Slam winning streak to 10 matches but not before a thorough workout from hitting partner Berankis, and he let his frustrations show during the 6-3, 6-4, 7-5 win.
The world number three trailed by a break of serve in the second set and appeared agitated at various stages, hitting his racquet on the court and yelling at his courtside box.
Murray served for the match at 5-4 in the third set but Berankis, the world number 110, broke back. But the 22-year-old dropped his next service game and Murray made no mistake in his second attempt at closing the victory.
The Olympic and US Open champion will next face the winner of the all-French affair between Monfils and Simon.
"I was struggling," Murray said. "He (Berankis) was making me feel pretty frustrated. We know each other well and we have practised together. He was making me feel pretty uncomfortable out there."
Williams unleashed her fastest ever serve, a 207 kilometres per hour (128 mph) bullet which equalled a speed clocked in round two against Garbine Muguruza, as she subdued the challenge of Morita.
"I feel today was actually a really good match for me," said Williams, a five-time winner at Melbourne Park and holder of 15 Grand Slam titles.
"I was involved in a lot of longer points, something I definitely wanted. I feel good. I hope I can keep this level up and go higher."
Azarenka admitted she needed to improve "everything" to successfully defend her title after surviving a scare against injured American Hampton, who winced as she played and was close to tears from the pain.
"It was definitely tough," said Azarenka, who won 6-4, 4-6, 6-2 and next plays Elena Vesnina. She is on course to meet Caroline Wozniacki in the quarter-finals.
"It's always good to know you can battle through not playing well, not feeling great."
World number seven Del Potro won four titles last year and dropped just 13 games in the first two rounds, but he found Chardy in inspired form and couldn't recover after going two sets down, finally succumbing in five.
Italy's Andreas Seppi ousted 12th seed Marin Cilic, but Tsonga found it easier with a straight-sets win over Blaz Kavcic, who was on an IV drip just two days ago after playing a five-hour marathon in intense heat.
In the prime-time evening match, four-time champion Roger Federer was due to play Australian upstart Bernard Tomic as he seeks to extend his record number of Grand Slam titles to 18.


Source: AFP