Victoria Azarenka has lost her second match in the WTA Championships in straight sets to Jelena Jankovic.
The two players, who both are former world number ones, took early breaks in the first set, but it was the seventh seed who managed to force a 5-4 lead before serving out the opener.
The Belarusian could not find her composure on serve in the second set, serving up six double faults to gift her opponent two breaks.
Azarenka also struggled as the Serbian's serve strengthened, allowing her to clinch the second set without facing a break point to secure a 6-4 6-3 victory.
