The top seed Sabine Lisicki of Germany was forced to retire injured in her ASB Tennis Classic quarter-final against compatriot Angelique Kerber, but two of the big names are still in the draw.
Kerber won the first set 6-4 and was up 4-3 in the second when Lisicki withdrew with an abdominal injury.
Kerber will play the fourth seed Flavia Pennetta in the semis, who showed why they call it moving day in tennis, Pennetta wasting no time showing Russian Elena Vesnina the exit, the Italian winning 6-2 6-1.
China's Zheng Jie also had little trouble in beating Lucie Hradecka of the Czech Republic, in straight sets winning 6-2 6-3 in just over an hour.
Third seed and two-time grand slam winner Svetlana Kuznetsova of Russia had too much class for Italy's Sara Errani winning 6-4 6-3 in the late match to decide the last semi-final berth.
In today's semi-finals, Pennetta has a shot at revenge for her 2011 US Open quarter loss to Kerber, while Jie faces Kuznetsova.