The match lasted 3 hours, 45 minutes before Halep finally took advantage of her first match point at 14-13, 40-30 when Davis sailed a forehand wide.
Halep failed to serve it out three times - at 5-4, 6-5 and 8-7 - before breaking the 24-year-old Davis in the 27th game of the 140-minute final set and holding for the remarkable victory.
Halep said that she now had nothing to lose for the rest of the tournament because "honestly, I thought it's over at that moment (three match points down)".
Halep left fans gasping in concern after rolling her ankle during her first-round win over Destanee Ajava, and even Halep admitted after beating Bouchard that she was anxious entering the match. So long. I never played a third set so long. "I'm very happy I could stay and win it.it was very nice we could show such good tennis". At Wimbledon in 2014, Bouchard defeated Halep in the semifinals before advancing to the final, where she lost to Petra Kvitova. "I don't know how my ankle is because I can't feel it any more".
Halep conceded she could not feel her dodgy ankle by the end of the match, which she injured in the first round of the tournament.
Not many players overpower Juan Martin del Potro, but Tomas Berdych did just that to win 6-3, 6-3, 6-2 and reach the fourth round of the Australian Open for the 10th time. Wozniacki had to save four break points while serving for the match but clinched it on her fourth match point.More news: EC recommends disqualification of 20 AAP MLAs to President
Yet to drop a set through her first three matches, Keys' big-hitting from the back of the court wore down the inexperienced Bogdan - playing in her maiden grand slam third round.
Davis was a career-high 26th in the world in May past year after winning her first WTA tournament in Auckland, before slipping to her current 76. Davis looked to be down-and-out especially coming into the encounter as the underdog and having lost the second set, she conceded ten straight points to go down 1-3 in the decider. "We were both fighting our hearts out", said the exhausted Davis. The third seed, Garbine Muguruza, splashed out in her second round match.
Keys missed last year's Australian Open after undergoing surgery to fix her injured left wrist. This was a high quality, dramatic duel which equalled the record number of games for a women's match in Melbourne (48) and lived up to the Shakespearean phrase,"though she be but little, she is fierce".
Lauren Davis played a part in Australian Open history Saturday and the unheralded American is determined to build on her performance, despite bowing out in memorable fashion at Melbourne Park. "But at 13-all, when I took the game, I said it's my lucky number, so it's going to be two in a row now".
Sixth seed Pliskova also had a tough test, beating fellow Czech Lucie Safarova 7-6 (8-6), 7-5.