- Samantha Stosur books her place in the semifinals at the WTA Championships
- Stosur crushes China's Li Na 6-1 6-0 to book meeting with Petra Kvitova
- Vera Zvonareva to face Victoria Azarenka in the other semi after Agnieszka Radwanska's defeat
- Radwanska fails in her bid to make last four after a straight sets defeat by Kvitova
U.S. Open champion Samantha Stosur stormed into the semifinals of the season-ending WTA Championships after crushing China's Li Na 6-1 6-0 in Istanbul.
Australian Stosur claimed the winner-takes-all contest in just 66 minutes, handing French Open champion Li her heaviest Tour defeat since a loss to Nadia Petrova in 2008.
The seventh seed has now won all six of her career meetings with the 29-year-old Li, five of which have come in straight sets, Stosur's latest success setting up a clash with Petra Kvitova.
"I'm very happy with the way I played," Stosur, who lost to Belarus' Victoria Azarenka on Wednesday, told the WTA's official website. "To come back from a disappointing loss in my last match and do this is great.
"Making it to the semifinals here last year will help me. I've learned a lot from all my previous experiences, so I'm hoping this year will be different.
"The semifinals are tough no matter what the circumstances. I'm not expecting an easy match. I hope I can play like I did tonight."
Stosur finished second in the White Group, while fourth seed Azarenka heads through as group winner and will face Vera Zvonareva in the semis.
Zvonareva qualified from the Red Group after Poland's Agnieszka Radwanska lost to Petra Kvitova in straight sets.
Needing to win one set to guarantee a semifinals berth, Radwanska was 5-1 up in the first set but eventually went down 7-6 6-3 to the 2011 Wimbledon champion, meaning Russia's Zvonareva went through by virtue of a better percentage of games won in the round robin stage.
Kvitova, from the Czech Republic, topped the group after winning all three of her matches, and said after her victory: "When I started today I was a bit confused. I didn't know what to do and was surprised Aga was moving so well.
"Luckily I was able to refocus. And the atmosphere today was unbelievable -- the people who came today were great, I hope they can come tomorrow too."