MELBOURNE, Australia (AFP) — Fired-up top seed Novak Djokovic powered into the Australian Open fourth round yesterday, joining sizzling fellow world number one Serena Williams and injury-free two-time winner Victoria Azarenka.

The Serb, whose chances of a fifth Australian crown have vastly improved after Roger Federer’s shock exit on Friday, ground down tenacious Spaniard Fernando Verdasco 7-6 (10/8), 6-3, 6-4.

He said he was highly motivated and over the virus that hampered his lead up to the season’s opening Grand Slam.

“Physically, I feel fit now and I’m always motivated to play well in Australia,” said Djokovic.

Williams, vying for a sixth Australian title and the first since 2010, was slow to get in the groove against 26th-ranked Ukrainian Elina Svitolina, going down 6-4 in the first set.

But she shook off the cobwebs under the blazing sun on Rod Laver Arena to rattle through the next two sets 6-2, 6-0.

It keeps alive her quest to add a 19th Grand Slam title, which would take her to clear second on the all-time Open Era Grand Slam winners list.

She currently has 18 alongside Chris Evert and Martina Navratilova, and is four behind German great Steffi Graf’s 22.

“When in doubt just start running as fast as you can, that’s what Venus always told me, that helped,” said Williams, whose world number one ranking is on the line if she fails to win the tournament.

She added that her elder sister’s late-career renaissance was an inspiration.

“She’s winning, she’s doing so well and I can do better. We always motivate each other. I’m so proud of her and we’re so excited.”

Venus rallied from behind to defeat Camila Giorgi of Italy 4-6, 7-6 (7/3), 6-1 to make the second week of a Grand Slam for the first time since Wimbledon 2011.

Azarenka, the champion in 2012 and 2013, who is unseeded this year after an injury-marred 2014 continued her impressive comeback, downing Czech 25th seed Barbora Zahlavova Strycova.

“There are things that obviously I want to improve. But it’s progress. It’s one step closer,” said the Belarussian after her 6-4, 6-4 win.

She next plays last year’s beaten finalist Dominika Cibulkova.

Defending men’s champion Stan Wawrinka, who beat Rafael Nadal in the final last year, could meet Djokovic in the semi-finals and stayed on track with a 6-4, 6-2, 6-4 victory over Finland’s Jarkko Nieminen.

The Swiss, who was always in control, was pleased with his progress.

Eighth seed Canadian Milos Raonic also went through, sweeping aside Germany’s Benjamin Becker in straight sets, while Japan’s fifth seed Kei Nishikori battled back from a set down to oust American Steve Johnson.

It was a day to remember for the Williams clan with the evergreen Venus setting up a fourth round clash with dangerous Pole Agnieszka Radwanska.

Radwanska defeated American Varvara Lepchenko 6-0, 7-5 and has doled out a dreaded 6-0 “bagel” to each of her three opponents at Melbourne Park.

She said she was looking forward to facing Venus, who she beat in the Montreal final last year.

“I think playing her is always a great challenge,” said Radwanska, who has made the quarter-finals or better in Melbourne on her last four visits.

Serena will now face Spain’s Garbine Muguruza, who beat Switzerland’s Timea Bacsinszky 6-3, 4-6, 6-0. The 24th seed ousted Serena at the French Open last year.