Russia's Alisa Kleybanova shocked defending champion Jelena Jankovic 6-4 6-3 to reach the semi-finals of the Kremlin Cup.
Despite the defeat, the second-seeded Serbian has already guaranteed her place in the upcoming season-ending WTA Championships in Doha, Qatar.
Kleybanova broke serve in the fifth game of each set, and victory was sealed when Jankovic double-faulted twice to lose the match.
She will now play Olga Govortsova, a 6-3 6-0 victor over Vera Dushevina, for a place in the final.
There were no such problems for number eight seed Francesca Schiavone, the Italian booking her place in the last four with a 6-3 6-2 win over Maria Kirilenko.
Schiavone, a runner up at the event in 2005, will next play Alona Bondarenko of Ukraine, who brushed past Bulgarian qualifier Tsvetana Pironkova 6-3 6-3.
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