Coco Gauff posted a rare victory over Iga Swiatek to punch her ticket to the semi-finals of the WTA Finals in Riyadh on Tuesday, ensuring Aryna Sabalenka will finish the year as the World No. 1. 

Swiatek, the defending champion, was in a direct battle with Sabalenka for the top spot this week but needed a win over Gauff to keep her chances alive of leapfrogging her Belarusian rival.