Vaidisova has already won six titles at the age of 17

The 17-year-old was playing in her first Grand Slam quarter-final after upsetting top seed Amelie Mauresmo in the fourth round on Sunday.

And Vaidisova's intensity helped her beat Williams in a fiercely competitive battle 6-7 (5-7) 6-1 6-3.

"Ive never been past the third round of a Grand Slam before," said Vaidisova.

"I'm so happy and excited now, I feel like screaming."

She added: "I just tried to be positive because I've played matches when I was negative after I lost the first set and then just lost the second as well."

FIVE LIVE VIEW Venus is Venus she can be amazing or she can be horrible PG Five Live: Have your say

Williams said: "I'll just work harder, obviously I'm disappointed. I would have loved to have done better."

Vaidisova will next face Svetlana Kuznetsova, who beat Dinara Safina 7-6 (7-5) 6-0.

Safina recovered from 5-1 down in the final set to beat Maria Sharapova in the previous round, and started in similar fashion against Kuznetsova.

But this time it was Safina who felt the pressure as she failed to serve out the set three times and missed a host of set points.

Kuznetsova was not at her best either but eventually took control, winning 13 of the last 14 games and reducing Safina to an embarrassing tally of just three points in the second set.

"I guess it was nerves, I just couldn't move," said Kuznetsova of her poor start. "Maybe it looked like I was not awake.