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.