Istanbul - Defending champion Serena Williams has made sure of a place in the semi-finals of the WTA Championships with a 6-2, 6-3 win over Petra Kvitova, the 2011 champion, on Thursday.
The American was relentlessly focussed against her gifted Czech opponent, who had led 4-1 in the final set when the two last met, eight months ago in a magnificent match in Doha, but Williams was never headed this time.
Then Kvitova's angular serving and flat hitting had done constant damage.
Now she was reduced to striking some good blows as an entertaining digression to the flow of heavy winners coming in the other direction.
It lasted only 72 minutes and it was Williams's third win in her group, leaving her with a day's rest before she seeks a place in the final by taking on the runner-up in the other group.
That could be Jelena Jankovic, Li Na, or Victoria Azarenka.