Tennis - Dubai Open - Women's Singles Final - Caroline Wozniacki of Denmark v Elina Svitolina of Ukraine - Dubai, UAE - 25/2/2017 - Elina Svitolina of Ukraine in action. REUTERS/Stringer - RTS10B6U

Tennis - Dubai Open - Men's Singles - Benoit Paire of France v Roger Federer of Switzerland - Dubai, UAE - 27/2/2017 - Benoit Paire in action. REUTERS/Ahmed Jadallah - RTS10NLR

Tennis - Dubai Open - Men's Singles - Guillermo Garcia-Lopez of Spain v Andy Murray of Great Britain - Dubai, UAE - 01/03/2017 - Guillermo Garcia-Lopez in action. REUTERS/Ahmed Jadallah - RTS10ZVE

Tennis - Dubai Open - Women's Singles - Caroline Wozniacki of Denmark v Catherine Bellis of the USA - Dubai, UAE - 23/2/2017 - Wozniacki in action. REUTERS/Ahmed Jadallah - RTS100O5

Tennis - Dubai Open - Women's Singles Final - Caroline Wozniacki of Denmark v Elina Svitolina of Ukraine - Dubai, UAE - 25/2/2017 - Elina Svitolina of Ukraine in action. REUTERS/Stringer - RTS10B6R

Tennis - Dubai Open - Men's Singles - Malek Jaziri of Tunisian v Andy Murray of Britain - Dubai, UAE - 28/2/2017 - Malek Jaziri in action. REUTERS/Ahmed Jadallah - RTS10TBZ

Tennis - Dubai Open - Men's Singles - Andy Murray of Britain v Malek Jaziri of Tunisia - Dubai, UAE - 28/2/2017 - Andy Murray in action. REUTERS/Ahmed Jadallah - RTS10TDV

Tennis - Dubai Open - Women's Singles - Angelique Kerber of Germany v Ana Konjuh of Croatia- Dubai, UAE - 23/2/2017 - Kerber in action. REUTERS/Ahmed Jadallah - RTS101DV

Tennis - Dubai Open - Men's Singles - Roger Federer of Switzerland v Benoit Paire of France - Dubai, UAE - 27/2/2017 - Roger Federer in action. REUTERS/Ahmed Jadallah - RTS10NI6

Tennis - Dubai Open - Men's Singles - Malek Jaziri of Tunisia v Andy Murray of Britain - Dubai, UAE - 28/2/2017 - Malek Jaziri in action. REUTERS/Ahmed Jadallah - RTS10TCZ

Tennis - Dubai Open - Women's Singles Final - Caroline Wozniacki of Denmark v Elina Svitolina of Ukraine - Dubai, UAE - 25/2/2017 - Elina Svitolina of Ukraine holds her trophy at the end of the match.

Tennis - Dubai Open - Women's Singles - Caroline Wozniacki of Denmark v Catherine Bellis of the USA - Dubai, UAE - 23/2/2017 - Bellis in action. REUTERS/Ahmed Jadallah - RTS100NW

Tennis - Dubai Open - Men's Singles - Roger Federer of Switzerland v Evgeny Donskoy of Russia - Dubai, UAE - 01/03/2017 - Roger Federer in action. REUTERS/Ahmed Jadallah - RTS110CQ

Tennis - Dubai Open - Men's Singles - Evgeny Donskoy of Russia v Roger Federer of Switzerland - Dubai, UAE - 01/03/2017 - Evgeny Donskoy in action. REUTERS/Ahmed Jadallah - RTS110Q0

Tennis - Dubai Open - Men's Singles - Benoit Paire of France v Roger Federer of Switzerland - Dubai, UAE - 27/2/2017 - Benoit Paire receives treatment. REUTERS/Ahmed Jadallah - RTS10NL9

Tennis - Dubai Open - Men's Singles - Roger Federer of Switzerland v Benoit Paire of France - Dubai, UAE - 27/2/2017 - Roger Federer in action. REUTERS/Ahmed Jadallah - RTS10NMW

Tennis - Dubai Open - Men's Singles - Andy Murray of Great Britain v Guillermo Garcia-Lopez of Spain - Dubai, UAE - 01/03/2017 - Andy Murray in action. REUTERS/Ahmed Jadallah - RTS10ZV3

Tennis - Dubai Open - Women's Singles - Caroline Wozniacki of Denmark v Catherine Bellis of the USA - Dubai, UAE - 23/2/2017 - Bellis in action. REUTERS/Ahmed Jadallah - RTS100NZ

Tennis - Dubai Open - Men's Singles - Roger Federer of Switzerland v Evgeny Donskoy of Russia - Dubai, UAE - 01/03/2017 - Roger Federer in action. REUTERS/Ahmed Jadallah - RTS110BQ

Tennis - Dubai Open - Men's Singles - Evgeny Donskoy of Russia V Roger Federer of Switzerland - Dubai, UAE - 01/03/2017 - Evgeny Donskoy in action. REUTERS/Ahmed Jadallah - RTS110D9

Tennis - Dubai Open - Men's Singles - Benoit Paire of France v Roger Federer of Switzerland - Dubai, UAE - 27/2/2017 - Benoit Paire in action. REUTERS/Ahmed Jadallah - RTS10NHC

Tennis - Dubai Open - Men's Singles - Andy Murray of Britain v Malek Jaziri of Tunisia - Dubai, UAE - 28/2/2017 - Andy Murray in action. REUTERS/Ahmed Jadallah - RTS10TEN

Tennis - Dubai Open - Men's Singles - Roger Federer of Switzerland v Evgeny Donskoy of Russia - Dubai, UAE - 01/03/2017 - Roger Federer leaves. REUTERS/Ahmed Jadallah

Tennis - Dubai Open - Women's Singles Final - Caroline Wozniacki of Denmark v Elina Svitolina of Ukraine - Dubai, UAE - 25/2/2017 - Caroline Wozniacki in action. REUTERS/Stringer - RTS10B5L