The American Danielle Collins, 37 of the WTA classification, deprived the Adelaide tournament of the first player in the world, the Australian Ashleigh Barty, which won in the round of 16 6-3 and 6-4 in just one hour of play.
The Swiss Belinda Becic and the Polish Iga Swiatek, second and fifth seeds, agreed instead to the quarterfinals comfortably and are now the top candidates to play the final.
Danielle Collins, 27, with no career titles, broke Barty's serve four times, enough to make up for the two times she gave up her serve.
The Australian had prevailed over the North American in their three previous matches.
Barty's elimination in the round of 16 from Adelaide follows her defeat in the Australian Open quarter-finals, where she lost to Czech Karolina Muchova. The possibility of a local player winning in Melbourne for the first time since 1978 was thus thwarted.
Collins saw cut his way through the first Grand Slam of the year in the second round.
The American now faces another major challenge in Adelaide, a few quarterfinals against the Polish Swiatek, who exhibited great solvency against the Australian Maddison Inglis and defeated her 6-1, 6-3 in an hour and a quarter.
Swiatek, winner of the last Roland Garros, did not lose her serve even once.
Belinda Bencic also did not find great opposition in her round of 16 rival, the Japanese Misaki Hoi, whom she defeated 6-1, 6-3.
Hoi had 12 breaking balls to question the strength of his rival, but he was only able to take advantage of two of them. In return, the Swiss took the service from him six times.
Bencic's opponent in the quarterfinals will be Australian Storm Sanders, who had a much harder time defeating Kazakh Yulia Putintseva, seventh favorite. After 2 hours and 18 minutes, he finally won 6-4, 5-7 and 6-1.
Another of the quarterfinals that was formed this Wednesday is the one that She will face the Latvian Anastasia Sevastova and the Swiss Jil Teichmann.
Sevastova eliminated the American Christina Mchale by 6-4 and 6-3, while Teichman suffered to defeat the eighth seed, China's Qiang Wang, 3-6, 6-3, 6-3.
Coco Gauff, also from the United States, emerged victorious from a three-set match, for the second consecutive round, and beat the Croatian Petra Martic 5-7, 6-3, 6-4. The 16-year-old will face her compatriot Shelby Rogers in the quarterfinals, who made her pass on Tuesday.