Djokovic advances

The top seed was simply irrepressible in serve, but struggled to find a break in Wawrinka's equally-impressive ability to hold and had to claim a tense tie-break 7-5 to win the opening set.

It appeared to be plain sailing in the second, but the straight sets victory came after an immense late fightback from the Swiss number two from 5-2 to an eventual 6-4 loss, finally breaking the Serb's service in the process after a double-break appeared to end his run in the tournament.

Djokovic will now meet compatriot Janko Tipsarevic after he beat France's Gilles Simon 7-6(3) 5-7 6-1 as he looks to retain the title he won in 2011.

Djokovic slammed the Manolo Santana centre court after his laboured second-round victory on Tuesday and joked that he was considering wearing football boots or enlisting the help of action star Chuck Norris to help deal with the slick surface.

He slipped and slid his way to a 7-6 6-4 win against unseeded Wawrinka on Thursday before announcing he would not play in the Spanish capital next year unless the red clay courts were reinstated.

"They are saying it's exactly the same as the red clay which is not true because there is a big difference," the Serb said.

"You are tripping and slipping and sliding all the time and winner will be the one who doesn't get hurt until the end of the week because a lot of players fell down," he added.

"Generally it's a new experience and the way it looks this year hopefully the last experience."