Second seed Clijsters found the Spaniard's game tricky to get to grips with and struggled to assert her game, making 39 unforced errors in total.

"It's always hard when you have a player who plays two totally different shots on each side," said Clijsters.

"You have to be ready to move and adjust all the time.

"A couple of times my footwork wasn't right and I wasn't playing how I should have been, but I'm happy I was able to move through."

Clijsters will now play Serb Ana Ivanovic for a place in the quarters after Ivanovic progressed at the expense of Virginie Razzano of France who was forced to retire while trailing 6-2 2-6 0-3 due to a thigh injury.

Elsewhere current French Open champion Francesca Schiavone defeated Llourdes Dominguez Lino of Spain 6-4 7-6 (7-2).

2009 champion Victoria Azarenka beat Dominika Cibulkova 3-6 6-3 6-4.

Vera Zvonareva and Agnieszka Radwanska also advanced.