Required to play two matches to make up for rain delays at Rogers Cup, Montreal Chinese Li Na first defeated Italian Sara Errani 6-4, 6-2 and then ousted second seeded Pole Agnieszka Radwanska 6-2, 6-1, who herself won 6-2, 6-4 against South African Chanelle Scheepers earlier in the day.

"I think the first match cost me a lot of power," Radwanska said. "It was very hot conditions out there, and then two hours later I was playing my second match. But anyway, she had the same situation, and she was playing too good. She was playing unbelievable today. I couldn't do anything."

Li Na next faces 16th seeded Czech Lucie Safarova in the semis, who defeated Roberta Vinci 6-2, 6-2.

"I've played her a few times. I don't think I've won against her yet," Safarova said. "She's a top player and always playing really strong. She has very strong groundstrokes. I have nothing to lose tomorrow. I will go there and try to play my tennis, try to take her time away and use my lefty serve, and we'll see."

Next semi-final will feature fifth seeded Petra Kvitova and seventh seeded Caroline Wozniacki.

Kvitova ousted Tamira Paszek 6-3, 6-2, and Wozniacki downed localite Aleksandra Wozniak 6-4, 6-4.