Madrid - Top seed Victoria Azarenka saw off China's Li Na wih a 3-6, 6-3, 6-3 battling win into the semi-finals of the Madrid Masters on Friday.
The Belarus world number one will await an opponent from Agnieszka Radwanska, the Polish fourth seed, and American qualifier Varvara Lepchenko.
Azarenka, January's Australian Open champion, levelled her record against Roland Garrrls holder Li at 4-4 with the victory.
Eighth seed Li, still looking for her first title of the season, lost for the seventh time in 2012 against 18 wins. She was playing her second clay quarter-final after Stuttgart.
Serena Williams won a battle of former number one players as she defeated second seed Maria Sharapova, the Stuttgart champion over Azarenka, 6-1, 6-3 with 11 aces, 28 winners and five breaks of serve in 80 minutes.
Azarenka said that after losing the opening set against Li, she still has no idea how she was able to turn the match around for victory in just under two hours.
"She played unbelievable in the first set," said the top seed. "I knew I had to do something.
"I don't know if it was confidence or self-belief or what. I don't know what happened but I managed I started to get into the match and build up my game."
The seed said that amid this week's controversy over the slickness of the new blue courts, the subject is not worth discussing until play is done.
"I see no reason to talk about the courts until after the event. These are the conditions we have to deal with."
Argentine tenth seed Juan del Potro won the first of the men's quarters as he put out Ukrainian Alexandr Dolgopolov 6-3, 6-4 in a 10-ace performance after winning last week's Estoril title on clay.