Sabine Lisicki caused a major upset in the third round of the Family Circle Cup by knocking out Venus Williams.

The German, seeded 16th, battled back after trailing in both sets to triumph 6-4 7-6 (7-5) after one hour and 27 minutes on court.

Lisicki broke her opponent's serve four times, the most crucial occasion coming when Williams was serving to level matters in the second set at 5-4.

The world number five then succumbed in a tie-break to tumble out of the tournament that she won on her maiden appearance back in 2004.

"I wasn't expecting that and, you know, I'll try to come back next year and win," she said. "I made a few errors at the wrong time and she played some great shots."

There were no such problems for Elena Dementieva, though, as the top seed cruised to a 6-1 6-1 victory over American Varvara Lepchenko.

The Russian recorded five breaks of serve to seal her place in the quarter-finals where she will face Dominika Cibulkova. The seventh seed battled back from a set down to defeat Anastasia Rodionova 6-7 (6-8) 6-2 6-3.

Caroline Wozniacki, the fifth seed who is chasing a second title in as many weeks, is also through to the last eight after a 6-3 6-4 result over Shuai Peng.

Sixth seed Marion Bartoli dispatched American qualifier Melanie Oudin 6-4 6-1.