Nadal ominous in Melbourne as Dimitrov gets back on track

Rafael Nadal stormed into the round of 16 at the Australian Open Friday with a vintage performance as Grigor Dimitrov and Caroline Wozniacki kept their Grand Slam hopes alive on a hot draining day.

But French Open champion Jelena Ostapenko's tournament is over, with the Latvian seventh seed crashing out in three sets to Estonian Annet Kontaveit.

Spanish world number one Nadal showed no mercy to 28th seed Damir Dzumhur on Margaret Court Arena, as he rediscovers his best form after ankle trouble.

The top seed raced through the match in just 1hr 50min, wasting as little energy as possible in the 6-1, 6-3, 6-1 rout.

"I was very, very focused," Nadal said. "I'm very happy with everything and to have another chance on Sunday."

That chance will be against 24th seeded Argentine Diego Schwartzman for a place in the quarter-finals.

Third seed Dimitrov, who could meet Nadal in the semis, had plenty to prove after a huge second-round fright from a qualifier, who pushed him to five sets.

And the Bulgarian delivered in a testing 6-3, 4-6, 6-4, 6-4 win over Russian rising star Andrey Rublev as temperatures touched 40 Celsius (104 Fahrenheit).

"These are the most important matches for me, when things are not working for me and I find a way," he said. "I'm feeling good physically, the heat didn't scare me at all today, so that's a good sign."

He will next face Australian Nick Kyrgios who beat French veteran Jo-Wilfried Tsonga in four close and entertaining sets in a prime-time evening match on Rod Laver Arena.

"It was amazing. I've never won a match on this court before but playing Jo I was obviously very nervous," said the 17th seeded local hope.

Second seed Wozniacki has not impressed so far, but she put in a better performance to beat Dutch 30th seed Kiki Bertens 6-4, 6-3, finally getting over the line on her fourth match point.

It sets her up with a clash against 19th-seeded Slovak Magdalena Rybarikova.

Fourth seed Elina Svitolina also kept her title dreams alive by ending the hopes of young teenage pretender Marta Kostyuk.

At just 15, Kostyuk was the youngest Melbourne Park third-round contestant since Martina Hingis in 1996. But she still has a lot to learn with fellow Ukrainian Svitolina handing out a 6-2, 6-2 lesson.

"She's definitely got a bright future," said Svitolina.

She now plays another qualifier -- big-serving Czech Denisa Allertova who romped past Magda Linette 6-1, 6-4 -- for a place in the quarter-finals on Sunday.

In a tournament shorn of seeds, 81st-ranked Petra Martic also swept into the round of 16, celebrating her 27th birthday by holding off a gritty three-set challenge from Thai qualifier Luksika Kumkhum.

Her reward is a match against Belgium's Elise Mertens, who beat struggling Alize Cornet of France in two tough sets.

Cornet was among players wilting in the heat, with a doctor taking her blood pressure early in the second set as she succumbed to the baking weather.

- Outdoor event -

No matches have been called off or roofs closed at the opening Grand Slam of the year despite the soaring temperatures, with tournament organiser Craig Tiley defending the decision.

"These are professional athletes," he said.

"We are at the end of the day an outdoor event. We want it to stay an outdoor event as long as possible but at the same time ensuring that the health and wellbeing of players is taken care of."

Organisers only activate the extreme heat policy when the temperature exceeds 40 Celsius and the wet bulb globe temperature index hits 32.5 Celsius.

On Thursday, Novak Djokovic described the conditions as "brutal", complaining it was hard to breathe.

Kyle Edmund joined Nadal in the round of 16, overcoming the elements in a fighting five-set win over Nikoloz Basilashvili.

Italian Andreas Seppi, Spanish 10th seed Pablo Carreno Busta, and Croatian sixth seed Marin Cilic also progressed.