Wimbledon, England -- (Sports Network) - Defending champion Venus Williams reached the quarterfinals at Wimbledon on Monday, but second seed Jelena Jankovic was not as fortunate, falling to Thai veteran Tamarine Tanasugarn.

The seventh-seeded Williams downed Alisa Kleybanova of Russia in straight sets, 6-3, 6-4, while Jankovic, of Serbia, was dominated by Tanasugarn, 6-3, 6-2, as the Thai reached her first career Grand Slam quarterfinal.

The women's draw has now lost its top-three seeds. World No. 1 Ana Ivanovic and former champion Maria Sharapova both exited the tournament last week.