After 10 consecutive holds, it was Halep who finally made the breakthrough, and this time, after three-hours, 45-minutes of play, she closed out the thrilling victory after Davis sent a forehand just wide.
"I'm nearly dead", Halep said of the match which equaled Chanda Rubin's win over Arantxa Shanchez Vicario in 1996 - also 48 games - for the Australian Open record in terms of most games. "So long. I never played the third set so long", said Halep, who will next Naomi Osaka after the Japanese player ended the hopes of Ashleigh Barty in straight sets.
The WTA's top-ranked player passed all tests with flying colors, cruising to a 6-2, 6-2 win over Eugenie Bouchard at Margaret Court Arena in Melbourne. "I think my second toes are just a bit infected", she said.
"I have no idea how much I run, I just know that my muscles are gone".
"I am always happy if I'm not the drama, and I feel like the U.S. Open I was the drama every night match that I played", Keys said. After a scintillating 225-minutes of play, world number one Simona Halep sneaked past the risky Lauren Davis in the third round of the 2018 Australian Open. But it was good because I relaxed my arm and I served pretty well those three points.
There are many similarities between Davis and Halep.
And Halep, already nursing an ankle injury after her first-round victory against Australian qualifier Destanee Aiava, was keen to bypass tennis talk.
Kerber's year-end ranking dropped from No. 1 in 2016 to 21 a year ago, when she failed to defend her Australian or U.S. Open titles.
Photo Davis taking a medical timeout in the third set against Halep. Maybe when she had the match balls, maybe I would have lost it.
Her proud fight wouldn't be enough, however, and Halep finished to seal her seventh win against Americans in eight matches since the start of last season, with solitary defeat coming against Rogers at 2017 Australian Open.
Caroline Garcia, the eighth seed, was forced the distance by Belarus' Aliaksandra Sasnovich but proved too strong with a 6-3 5-7 6-2 success and will next meet American 17th seed Madison Keys. Look for Halep and Wozniacki to remain the favorites going into the second weekend.
"It was very hard", Davis said.
Davis, the 24-year-old who has never passed the third round of a major, had three chances to close it out when returning at 11-10, and openings on the first two points she could not quite take.
The women's draw has already lost Garbiñe Muguruza, the No. 3 seed and the defending Wimbledon champion; Venus Williams, the No. 5 seed who was the runner-up here past year; and Jelena Ostapenko, the No. 7 seed and the defending French Open champ.