World number one Simona Halep survived an epic battle with unseeded American Lauren Davis to reach the Australian Open fourth round.

The Romanian, 26, had to save three match points in the decider before eventually winning 4-6 6-4 15-13 after three hours and 45 minutes.

The final set lasted 142 minutes before Halep finally served out the match at the fourth attempt.

“I never played a third set so long. I’m almost dead,” she said.

“My muscles are gone. I don’t know how my ankle is because I can’t feel it any more.”

The contest equalled the women’s singles Australian Open record for longest match in terms of games played, tying the 1996 quarter-final between Chanda Rubin Arantxa Sanchez Vicario, which Rubin won 6-4 2-6 16-14.

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Halep served for the match at 5-4, 6-5 and 8-7 in the third set but was denied and later recovered from 0-40 on her own serve with the score 11-10 to the impressive world number 76 Davis.

“Honestly, I thought it’s over at that moment, but was good because I relaxed my arm and I served pretty well those three balls,” said Halep.

“It was not easy, but I just kept playing. I just kept believing that it’s not over, even if she’s leading a little bit more.

“I gave everything I had today, and actually, I’m really proud that I could stay there and win it. It was not easy at all. She played great.”

She will play Naomi Osaka in the last 16 after the Japanese player beat Australian 18th seed Ashleigh Barty 6-4 6-2.

‘Incredible warriors’ go through pain barrier

Davis was twice treated for a toenail injury in the latter stages while Halep, who had an ankle problem in the opening rounds, was also limping and holding her upper leg.

Asked if her toenail came off, Davis said: “It’s about to.

“It was very difficult. I had never really had that happen before. I couldn’t really put any pressure on them.”

The 24-year-old added: “That third set was nothing really like I had ever played before. We were both fighting our hearts out.

“Every point was just super long. I got to the point where I was so tired I just told myself to swing and move, and for the most part it was very effective.”

American former Grand Slam winners Chris Evert and Tracy Austin praised both players after the match.

“So impressed with the great effort from Lauren Davis and Simona Halep. Both deserved to win that match,” 18-time Grand Slam singles champion Evert said.

Austin, a two-time US Open winner, said: “Simona Halep and Lauren Davis are incredible warriors! Both ladies should be so proud. Kept digging deeper when it looked like there was nothing left in the tank!”

Pliskova through in straight sets

Elsewhere, Czech sixth seed Karolina Pliskova beat compatriot Lucie Safarova 7-6 (8-6) 7-5 to reach round four.

French eighth seed Caroline Garcia came through in three sets 6-3 5-7 6-2 against Belarus’ Aliaksandra Sasnovich.

She will play American 17th seed and 2017 US Open runner-up Madison Keys who progressed with a 6-3 6-4 win over Romania’s Ana Bogdan.

World number seven Jelena Ostapenko was beaten by Estonia’s Anett Kontaveit in the third round of the Australian Open.

The French Open champion suffered a 6-3 1-6 6-3 defeat by world number 33 Kontaveit in one hour and 53 minutes.

Kontaveit, who has reached the fourth round for the first time in Melbourne, will next play Spain’s world number 39 Carla Suarez Navarro.

Elsewhere, second seed Caroline Wozniacki reached the last 16 with a straightforward win over Kiki Bertens.

Wozniacki beat her Dutch opponent 6-4 6-3, saving four break points in the final game before serving out the match.

The Dane will next face Slovakia’s Magdalena Rybarikova.

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Ostapenko’s exit means that Angelique Kerber and Maria Sharapova – who play each other on Saturday – are the only two Grand Slam champions remaining in the women’s draw.

There were 11 double faults in a scrappy affair on Margaret Court Arena, with Latvia’s Ostapenko losing all five of her service games in the first set.

Ostapenko took a medical timeout before the second set for treatment on her thigh and she found enough rhythm to take the game into a third set.

Despite some solid defence from Ostapenko, Kontaveit got the decisive break before winning eight of the final 10 points of the match to claim victory.

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Nick Kyrgios kept home hopes very much alive in the men’s singles at the Australian Open with victory over France’s Jo-Wilfried Tsonga.

The 22-year-old 17th seed beat 15th seed Tsonga 7-6 (7-5) 4-6 7-6 (8-6) 7-6 (7-5) in the third round.

Kyrgios goes on to face Bulgarian third seed Grigor Dimitrov in the last 16.

On a day when temperatures peaked in the afternoon at 40.2C, Kyrgios benefited from playing in the cooler night session.

Tsonga, 32, was one of the Australian’s childhood heroes and a finalist in Melbourne 10 years ago.

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The Frenchman gave a serious examination of the man most likely to end Australia’s 32-year wait for a male champion, but Kyrgios held his nerve impressively in three tie-breaks.

“He is a great guy, a champion of the game, someone I looked up to as a kid,” said Kyrgios of his opponent afterwards.

“To be in the locker room with these guys, the first year especially, was surreal.

“Grigor Dimitrov is an amazing athlete who finished the year strongly last year, and the best-of-five sets might suit him. It will be a tough match.”

The margins were slim between two of the game’s bigger servers – both men finished with 28 aces – a Tsonga double-fault handing over the first set, before a delicate drop shot earned him the only break of the second.

Both had their chances in the crucial third set tie-break but it was Kyrgios who took his first opportunity with a backhand return.

Break points went begging early in the fourth, with Kyrgios finding a superb second serve under pressure at 30-30, 4-5, before Tsonga looked to be forcing a fifth set when he led 5-2 in the third tie-break.

A knee issue then looked to disrupt him and Kyrgios took full advantage, reeling off five points in a row to seal victory.

Tsonga was asked after the match about an altercation he had with a spectator in the third set, which prompted a furious response from the Frenchman.

“The guy was talking to me and telling me, ‘You are under pressure now, you are under pressure now,’ when I was bouncing my balls,” he said.

“That’s it. I lost it and I drive a little bit crazy. You know, it’s not fair. It’s not fair. But that’s it.

“The guy was feeling safe because he was upstairs. I just tell him, ‘Come now to see if you feel the pressure or not.’ That’s it.”

‘The heat didn’t scare me’

Dimitrov earlier came through a tough match against 30th seed Andrey Rublev in the heat of the afternoon.

The Bulgarian needed over three hours to win 6-3 4-6 6-4 6-4 on Rod Laver Arena.

“These are most important matches when things are not working and I am able to find a way,” Dimitrov, 26, said.

“Physically I am feeling good and the heat didn’t scare me. That is a good sign.”

Asked about the prospect of facing Kyrgios, and the majority of the crowd, Dimitrov said: “I’ve done it many times before.

“I’ve played against the local, so to speak. That’s part of the game.”