Realistically, no one expected drama in this match, and certainly not to this extent.
Halep is playing in her first major tournament as the No. 1 player in the world rankings and is seeking her first Grand Slam title.
Along the way, he has won five of his 19 Grand Slam singles titles here.
However, she was proud of her efforts on an epic night at Melbourne Park.
Women's No. 1 Simona Halep took a longer route - equaling a mark in Melbourne for endurance but signaling, perhaps, that she's closer to a Grand Slam breakthrough. "I got to the point where I was so exhausted where I just told myself to swing and move, and, I mean, for the most part it was very effective".
"Was very tough match". Because I didn't really feel any pressure or anything.
"I definitely felt that way", said Keys, who made a run to the Open semi-finals as a teenager in 2015. "She's a confident player at the moment".
"I gave her the confidence by making a lot of errors on the return games", Sharapova said. "Looking at the overall picture - the beginning of this year - there's a lot to build from".
Their first meeting came at the Australian Open in 2012, when Sharapova beat Kerber in the third round in straight sets.
Halep had chances to serve for the match in the ninth, 11th and 15th games of the third set but was broken each time by the No. 76-ranked Davis, who then blew three match points from 0-40 on Halep's serve in the 22nd game.
On the the three match points she faced against Davis - who lost a toenail in the final set - Halep continued: "I thought it's over at that moment, but it was good because I relaxed my arm and I served pretty well those three balls".
Both players had emptied the tank by this stage, with Davis needing two medical time-outs for treatment on both of her feet, before Halep secured a break at 13-13 before serving out the match in the next game.
Flying under the radar, the 17th seed has surrendered just 16 games on her way to the fourth round after beating Romania's Ana Bogdan 6-3, 6-4.
She will next test herself against French eighth seed Garcia, who was too strong for Belarussian Alaksandra Sasnovich, winning in three sets.
Among the seeded men advancing were No. 6 Marin Cilic, who beat Joao Sousa 6-1, 7-5, 6-2, and No. 10 Pablo Carreno Busta, who was leading 6-2, 3-0 when Gilles Simon retired from their second-round match with a thigh injury.
Six-time champion Novak Djokovic is through to the Australian Open's fourth round after a 6-2, 6-3, 6-3 win over Albert Ramos-Vinolas. "I played really, really well". His defense moved through another round with a 6-2, 7-5, 6-4 win over No. 29 Richard Gasquet. In the subsequent match on Rod Laver Arena, Hyeon Chung beat fourth-seeded Alexander Zverev in five sets.
Another loss at a major had the highly-touted Zverev admitting he may have a problem. "So it's going to be two in a row now", Halep said with a smile. He lost both five-setters he played past year at the majors to Tomas Berdych at Wimbledon and to Juan Martin del Potro at the U.S. Open.