Catherine Bellis of the US hits a return to Shelby Rogers of the US on the third day of the US Open Tennis Championships at the USTA National Tennis Center in Flushing Meadows, New York, USA, 31 August 2016. The US Open runs through September 11. EPA/PETER FOLEY

Naomi Osaka of Japan hits a return to Ying-Ying Duan of China on the third day of the US Open Tennis Championships at the USTA National Tennis Center in Flushing Meadows, New York, USA, 31 August 2016. The US Open runs through September 11. EPA/ANDREW GOMBERT

Johanna Konta of Great Britain hits a return to Tsvetana Pironkova of Bulgaria on the third day of the US Open Tennis Championships at the USTA National Tennis Center in Flushing Meadows, New York, USA, 31 August 2016. The US Open runs through September 11. EPA/RAY STUBBLEBINE

Caroline Wozniacki of Denmark hits a return to Svetlana Kuznetsova of Russia on the third day of the US Open Tennis Championships at the USTA National Tennis Center in Flushing Meadows, New York, USA, 31 August 2016. The US Open runs through September 11. EPA/JOHN G. MABANGLO

Anastasija Sevastova of Latvia (R) reacts after defeating Garbine Muguruza of Spain (L) on the third day of the US Open Tennis Championships at the USTA National Tennis Center in Flushing Meadows, New York, USA, 31 August 2016. The US Open runs through 11 September. EPA/DANIEL MURPHY