Top seed Serena Williams and her older sister Venus led a foursome of American women into the Australian Open fourth round yesterday, while men’s top seed Novak Djokovic survived a nervous start to overcome Fernando Verdasco.

It is the first time four women from the traditional tennis powerhouse, which has relied on the Williams sisters for much of their grand slam success in the past decade, have made the last 16 at a major since Roland Garros in 2013.

The sisters were joined in the last 16 by the two Madisons – Brengle and Keys – who will play each other – with the 19-year-old Keys upsetting twice Wimbledon champion Petra Kvitova 6-4 7-5.

“I think my hands are still shaking,” said Keys, who is coached by former number one Lindsay Davenport. “I’m excited to play Maddie in the next round.”

Twice champion Victoria Azarenka also advanced after a 6-4 6-4 victory over 25th seed Barbora Zahlavova Strycova and will now meet last year’s beaten finalist Dominika Cibulkova.

With Roger Federer’s surprise exit on Friday still hanging over the tournament, the men’s favourites had some nervous moments in their third round clashes yesterday.

Djokovic was forced into a first set tiebreak by former top-10 player Verdasco, while fifth seed Kei Nishikori also dropped the first set tiebreak before he beat Steve Johnson.

Johnson and 19th-seed John Isner, who was beaten by Luxembourg’s Gilles Muller, were the last American men in the singles competition, though North America will be represented in the fourth round by Canada’s Milos Raonic.

Djokovic’s match, which was temporarily halted before the third set as Verdasco took a time-out, did have another distraction with a marriage proposal in the stands that the world number one applauded when the woman accepted.

“I’m sure he was very happy when she said yes,” a smiling Djokovic said. “It’s nice to see this moment.”

Men’s champion Stan Wawrinka, pleased to be out of the glare of many people, also continued his quiet progression with a clinical victory over Jarkko Nieminen.

“I’m not the focus of the tournament because there’s Novak, Rafa coming back from injury, Roger also just lost, there’s Kyrgios, Tomic still playing,” Wawrinka said.

While Azarenka continues to lurk as a danger to anyone in the top half of the draw, an ominous portent developed over the rest of the women’s field with the Williams’ sisters success.

The last time the siblings reached the last 16 at Melbourne Park, Serena went on to win her fifth Australian Open title.

It was also the last time the 18-times grand slam winner lifted the Daphne Akhurst Memorial Cup.

The world number one beat Ukraine’s Elina Svitolina 4-6 6-2 6-0, while Venus also needed a set to get going before she beat Italy’s Camila Giorgi 4-6 7-6(3) 6-1 to make her first grand slam fourth round since Wimbledon 2011.

“That feels fantastic especially when things happen in your life that are not in your control,” said Venus, who struggles with Sjogren’s syndrome, an auto-immune disease that can cause joint pain and fatigue.

“But I don’t want to stop now, I want to keep it going.”

The 34-year old will now meet women’s sixth seed Agnieszka Radwanska who also continued her untroubled progress with a 6-0 7-5 win over another American Varvara Lepchenko, while Serena will play the enigmatic Garbine Muguruza.

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