Sabine Lisicki of Germany (L) celebrates after defeating Serena Williams of the US (R) during their women's singles tennis match at the Wimbledon Tennis Championships, in London, July 1, 2013. [Photo/Agencies]

After dropping just 11 games in the first three rounds, her surprise exit, which mirrored those of former men's champions Roger Federer and Rafa Nadal last week, ended Williams's win streak at 34 matches. It was only her fourth loss in the last 76.

"She played a super aggressive game. When you're playing and you have absolutely nothing to lose, it's like you can really play with so much freedom and so loose. That's how she played today," Williams told reporters.

"I didn't play the big points good enough. I didn't do what I do best. I think I had a little hesitation, and that explains it."

Lisicki took advantage of a somewhat sluggish Williams to seize the first set, her strong serve and fizzing groundstrokes at times leaving the multiple Grand Slam winner rooted to the spot.

The American, aghast, annoyed and berating herself after each error, desperately searched for the missing aggression and from 1-0 down in the second, reeled off nine games in a row.

She made no unforced errors to breeze through the second set and appeared to have knocked the stuffing out of her reeling opponent.

But the doubts began to creep back into her game as each time she appeared to be in control, the German answered with breaks of her own before Williams dropped her serve to trail 5-4.

Williams saved one match point, then wasted a break point of her own before Lisicki sealed the biggest victory of her career with a rasping forehand winner.