Wimbledon finalist Agnieszka Radwanska was the biggest casualty on a marathon day at the rain-hit Roger's Cup in Montreal.
Second seed finds Li Na too strong in Toronto
Wimbledon finalist Agnieszka Radwanska was the biggest casualty on a marathon day at the rain-hit Roger's Cup in Montreal.
The second seed had beaten Chanelle Scheepers of South Africa 6-2 6-4 in her third round match earlier in the day but had no answer to Li Na in the last eight, going down 6-2 6-1.
Li, who has lost finals in Sydney and Rome this year, overcame eighth seed Sara Errani in an earlier match and will now face Czech Lucie Safarova for a place in the final.
"I think I played unbelievably well for both matches," said the former French Open champion.
Safarova had the luxury of playing just one match on Saturday, easing past Roberta Vinci 6-2 6-2.
Fifth seed and compatriot Petra Kvitova beat Tamira Paszek 6-3 6-2 to book a semi-final clash with seventh ranked Caroline Wozniacki.
The Dane struggled past Varvara Lepchenko of the United States 4-6 6-3 6-4 before returning four hours later to see off a stubborn Aleksandra Wozniak 6-4 6-4 after the Canadian saved five match points.
"It was tough today, two tough, long matches," she said. "Kvitova has been playing great this week. She is a great player and it is not going to be easy. I am just looking forward to getting a good night's sleep."
Both the semi-finals and the final are scheduled to take place on Sunday.
