Simona Halep is the No. 2 seed at the United States Open and has more hardcourt victories this year than any other woman in the main draw, compiling a 35-5 record.
But she had never reached the Open quarterfinals until Monday, when she escaped a sloppy match on a scorching Louis Armstrong Stadium court with a 6-7 (6), 7-5, 6-2 victory over No. 25-seeded Sabine Lisicki.
No. 20 Victoria Azarenka, whom many consider the player most capable of beating Serena Williams, also advanced to the quarterfinals with a 6-3, 6-4 victory over Varvara Lepchenko of the United States.