Victoria Azarenka wins gruelling WTA Championships opener

Victoria Azarenka has won her opening match of the WTA Championships in Istanbul thanks to a tough straight-sets victory over Sara Errani.

The world number two looked down and out in the first set as she fell 2-5 behind, but Errani failed to serve it out three times before Azarenka fought back to force the tie-break.

The Belarusian then went on to clinch the tie-break 7-4 with an energy-sapping 90 minutes on the clock.

Both players exchanged breaks at the start of the second, but it was Azarenka who took advantage of a waning Errani by breaking the Italian twice more to close out the match 6-2.