Toronto third seed seed Venus Williams suffered a shock second-round defeat to qualifier Kateryna Bondarenko.

After being given a bye in the first round, Venus surrendered a first-set lead before going down 1-6, 7-5, 6-4 to the Ukrainian underdog.

Venus Williams powered through the first set before losing all concentration in the second and third sets.

Bondarenko's pressure increased right up until match point with Venus Williams left distraught at defeat.

Sister Serena Williams will face Yaroslava Shvedova in the Toronto second round after Shvedova beat Daniela Hantuchova 7-6 (7/1) 7-6 (7/4) in the first round.

Meanwhile, Kim Clijsters continued her comeback after a two-year absence with a 6-3 6-4 first-round victory over Britain's Elena Baltacha.

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