MELBOURNE, Australia -- In what was the third-longest Australian Open women's match in the Open Era, No. 1 Simona Halep outlasted unseeded American Lauren Davis 4-6, 6-4, 15-13 after a three-hour, 44-minute match.
The final set took two hours and 22 minutes to complete.
Halep served the match four times and saved three match points in the 22nd game of the third set at 0-40. Davis saved five break points in the 23rd game.
The No. 76-ranked Davis had two medical time outs in the third set for blisters on both feet.
"Definitely was a very tough match, so long," said Halep, who has twice reached the final at the French Open but never won a Grand Slam singles title. "I never played the third set so long, so I'm really happy I could stay and win it. I'm almost dead."
"I just feel that my muscles are gone. My ankle is, I don't know how it is because I don't feel it anymore, but it was nice to be on court. It was nice to win this match."
Davis did everything possible to stay in the match, keeping long rallies alive to put pressure on Halep.
She finished with roughly twice the number of winners (52 to 27) against slightly more than double the unforced errors (73-39) and broke Halep's serve six times.
Halep will play the winner of Saturday's match between Ashleigh Barty and Naomi Osaka. Davis falls to 0-4 in third-round matches at majors.
U.S. Open finalist Madison Keys advanced 6-3, 6-4 over Ana Bogdan and will next play No. 8 Caroline Garcia, who beat Aliaksandra Sasnovich 6-3, 5-7, 6-2.
Sixth-seeded Karolina Pliskova had 11 aces and beat No. 29 Lucie Safarova 7-6 (6), 7-5 in a match featuring just one service break.
The 17th-seeded Keys, who lost in the U.S. Open final last year to Sloane Stephens, saved three break points serving for the match, finally clinching it on her first match point when Bogdan netted a backhand.
Keys missed last year's Australian Open after undergoing surgery to repair her injured left wrist. She then played only one match after the U.S. Open before shutting down her season early to let the wrist heal. It's helped her start the new season feeling mentally fresh, as well.
"I finished the U.S. Open and I was exhausted," she said. "So as amazing as that run was, the combination of being exhausted from that and having a wrist that still wasn't 100 percent perfect, I just needed to kind of shut it down, calm down, and then I was really excited to start the new season."
Keys is the only one of the four American women who reached the semifinals at the U.S. Open last September still in contention in Melbourne -- Stephens, Venus Williams and CoCo Vandeweghe were all eliminated in the first round.
Information from the Associated Press was used in this report.