Petra Kvitova has made it through to the semi-finals of the WTA Championships with a straight-sets victory over Caroline Wozniacki.
After a tired performance lost her the first set 6-4, the world number one needed her blood pressure checked courtside but was given the all-clear to continue.
However, Azarenka capitalised on her opponent's ailing fitness and took the second 6-2.
The Wimbledon champion will be joined by Victoria Azarenka in the final four after her win against Li Na.
