Top seed Ana Ivanovic had her serve broken five times as she lost to Amelie Mauresmo in the Brisbane International.
Former Australian Open and Wimbledon champion Mauresmo dropped serve just once on her way to a 6-3 6-2 quarter-final victory.
Mauresmo's first break of serve gave her a vital 5-3 lead in the first set.
Ivanovic recovered from a second set break before Mauresmo rattled off four games in a row to secure her sixth win in eight matches against the Serbian.
The fifth seed will now play Marion Bartoli of France in the semi-final, after she overcame Italy's Tathiana Garbin 6-3 6-3.
Earlier, second seed Victoria Azarenka of Belarus lost three of her first four service games before turning things round to beat Lucie Safarova 7-6 (7-5) 6-4 and book a semi-final against Sara Errani who beat Olga Govertsova 6-3 6-3.
In the men's draw, third seed Fernando Verdasco came from a set down to beat Florent Serra 4-6 6-0 6-3.
Verdasco dropped serve in the ninth game but bounced back well to take the second set in just 26 minutes.
He saved break point at 30-40 in the fifth game of the third set and from that point wasted little time in wrapping up the win.
His semi-final opponent will be Paul-Henri Mathieu, who beat 19-year-old Japanese player Kei Nishikori 6-3 6-4.
Elsewhere, Slovakia made it through to the Hopman Cup final after a win over Germany which followed a serious-looking ankle injury for Australian Open hopeful Nicolas Kiefer.
Kiefer, 31, was leading 3-1 in the first set against Slovakia's Dominik Hrbaty in Perth when he twisted his ankle and was taken off the court in a wheelchair.
That gifted the tie to Slovakia, who advanced to Friday's final as Dominika Cibulkova had earlier beaten Sabine Lisicki 7-6 6-4 in the women's singles match.
Russia await them in the final after they beat France 2-1.
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