Australian Open: Djokovic joins Serena, Wawrinka in last 16

Melbourne: Novak Djokovic eased into the fourth round at the Australian Open with a straight sets win over Spain`s Fernando Verdasco on Saturday. The Serb world number one beat the 31st seeded Verdasco 7-6 (10/8), 6-3, 6-4 in 2hr 21min and will play Luxembourg`s Gilles Muller in the next round.

World number one Serena Williams took time to wake up before sizzling into the fourth round, joining resurgent sister Venus and the dangerous Agnieszka Radwanska.

The American top seed, 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 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."

Defending champion Stan Wawrinka reached the fourth round of the Australian Open with a straight sets win over Finland`s Jarkko Nieminen on Saturday.

The Swiss fourth seed cruised through 6-4, 6-2, 6-4 in 1hr 49min on Rod Laver Arena and will play either Spain`s Guillermo Garcia-Lopez or Canada`s Vasek Pospisil in the round of 16.

Women`s fourth seed Petra Kvitova and men`s fifth seed Kei Nishikori are also in action, while eighth seeded Canadian Milos Raonic swept aside Germany`s Benjamin Becker in straight sets.

Canada`s eighth seed Milos Raonic smashed 22 aces on the way to a straight sets demolition of Benjamin Becker to reach the fourth round at the Australian Open on Saturday.

The big-serving Raonic defeated Becker 6-4, 6-3, 6-3 in 1hr 41min on Hisense Arena to ease into the round of 16 and will face either Poland`s Jerzy Janowicz or Spanish 12th seed Feliciano Lopez next.

The victory means Raonic has equalled his best performance at Melbourne Park after reaching the round of 16 as a qualifier in 2011.

He served at 71 percent and clocked a fastest serve at 225 kph (181 mph) among the many thunderbolts he hurtled down to the German.

The Canadian hit 46 winners and only 19 unforced errors, while Becker made just 21 winners.

"I feel like I am getting better each match, I`m having a lot of fun, I`m enjoying the atmosphere and I`m looking forward to keep going," said Raonic, who was the first Canadian since 1908 to reach a Grand Slam semi at Wimbledon last year.

"It`s a great time for Canadian tennis, I`m grateful to be a part of it and let`s keep changing those dates, let`s keep breaking new records."

Becker, whose serve was broken five times, showed little threat to Raonic after coming from behind to eliminate Australian dual Grand Slam champion Lleyton Hewitt in five sets in the previous round.

It was a day to remember for the Williams clan with Venus making the second week of a Grand Slam for the first time since Wimbledon 2011.The evergreen 34-year-old battled back from behind to defeat Camila Giorgi of Italy 4-6, 7-6 (7/3), 6-1 and set up a fourth round clash with Radwanska.

"That feels fantastic, especially when you have things happen in your life which are out of your control," said Venus, a seven-time Grand Slam winner who has had a long battle with the energy-sapping Sjogren`s Syndrome.

"I don`t want to leave it at that, I`ll try to keep going," she added, clearly enjoying the moment in front of an appreciative crowd on Margaret Court Arena.

Poland`s 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 this year, lurking as a dangerous dark horse.

She said she was eagerly 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. 

"I think she is still playing great tennis even she`s a bit older. She`s still really fit and playing a high level. I think it`s going to be another good match."

Serena will next face Spain`s Garbine Muguruza, who overcame a mid-match stumble to beat Switzerland`s Timea Bacsinszky 6-3, 4-6, 6-0.

The 24th seed beat Serena at the French Open last year and said she was up for the challenge again in Melbourne.

"I think I don`t have nothing to lose. I don`t think I have pressure," she said. "I like to play big matches on centre court, so I`m just really happy that I can play against her."

Two-time champion Victoria Azarenka continued her comeback with a straight sets win over Barbora Zahlavova Strycova to reach the last 16. She downed the Czech 25th seed 6-4, 6-4 to set up a fourth round meeting with last year`s finalist Dominika Cibulkova, seeded 11. Former world number one Azarenka, 25, is unseeded this year as she returns from a horror 2014 which saw her battling injury and depression as her ranking slid to 44.

Japan`s fifth seed Kei Nishikori battled back from a set down to oust American Steve Johnson and reach the last 16. Nishikori won 6-7 (7/9), 6-1, 6-2, 6-3 in 2hr 29min on Hisense Arena and will face either Spain`s David Ferrer or French 18th seed Gilles Simon in the fourth round.

The 25-year-old, a superstar at home, was nervous in the opening set before a cheering pro-Japanese crowd, but he gradually wore down the 38th-ranked American to reach the round of 16 for the fourth straight year. The US Open finalist served at 65 percent, hit 49 winners and made 24 unforced errors and only lost his serve once in a dominant performance.

Nishikori broke Johnson`s serve seven times and was helped along by the American double-faulting nine times.

"It was a nice battle and I was playing solid in the last couple of sets, so it was a very good win today," Nishikori said.

"I was a little bit nervous early but I started to get the rhythm and started to play solid, so I am very happy to go through.

"I think from now on it will be a tougher opponent coming up, but I`ve won three good matches so it was exciting to play here today."