Angelique Kerber of Germany plays a forehand in her semi-final match against Carla Suarez Navaro of Spain during Day 6 of the 2016 Brisbane International at Pat Rafter Arena on January 8, 2016. Chris Hyde / Getty Images
Andy Murray of Great Britain serves to Alexander Zverev of Germany in the men’s singles match during Day 6 of the 2016 Hopman Cup at Perth Arena on January 8, 2016. Paul Kane / Getty Images
Illya Marchenko of Ukraine in action against Rafael Nadal of Spain during their semi-final match for the Qatar ATP Open tennis tournament at the Khalifa Tennis Complex in Doha on January 8, 2016. EPA
Victoria Azarenka of Belarus plays a backhand in her semi-final match against Samantha Crawford of the United States during Day 6 of the 2016 Brisbane International at Pat Rafter Arena on January 8, 2016. Chris Hyde / Getty Images
Rafael Nadal of Spain returns the ball to Illya Marchenko of Ukraine during their semi-final match at the Qatar Open tournament on January 8, 2016, in Doha. Nadal won 6-3, 6-4. KARIM JAAFAR / AFP
Heather Watson of Great Britain serves to Sabine Lisicki of Germany in the women’s singles match during Day 6 of the 2016 Hopman Cup at Perth Arena on January 8, 2016. Paul Kane / Getty Images
Nick Kyrgios of the Australia Green team hits a return against Kenny de Schepper of France during their 12th session men’s singles match on Day 6 of the Hopman Cup at Perth on January 8, 2016.Tony Ashby / AFP
Roger Federer of Switzerland serves the ball to Grigor Dimitrov of Bulgaria during their quarter-final match at the Brisbane International Tennis Tournament on January 8, 2016. EPA/DAVE HUNT AUSTRALIA AND NEW ZEALAND OUT
Dominic Thiem of Austria hits a return against Marin Cilic of Croatia during their men’s singles match on the sixth day of the Brisbane International tennis tournament on January 8, 2016. Saeed Kkhan / AFP
Grigor Dimitrov of Bulgaria returns the ball to Roger Federer of Switzerland during their quarter-final match at the Brisbane International on January 8, 2016. Dave Hunt / EPA
Bernard Tomic of Australia reacts after winning a point in his quarter-final match against Kei Nishikori of Japan during the Brisbane International on January 8, 2016. Tertius Pickard / AP Photo
Alison Riske of the United States hits a return against Timea Babos of Hungary during their singles semi-final match at the Shenzhen Open WTA tennis tournament in southern China’s Guangdong province on January 8, 2016. AFP
Sabine Lisicki of Germany covers her head during a break against Heather Watson of Britain during their women’s singles match on Day 6 of the Hopman Cup on January 8, 2016. Tony Ashby / AFP-IMAGE RESTRICTED TO EDITORIAL USE - NO COMMERCIAL USE
Kenny De Schepper of France returns a ball to Nick Kyrgios for Australia Green during their men’s singles match on Session 12 on day 6 of the Hopman Cup at the Perth Arena on January 8, 2016. Tony McDonough / EPA
Kei Nishikori of Japan plays a shot in his quarter-final match against Bernard Tomic of Australia during the Brisbane International on January 8, 2016. Tertius Pickard / AP Photo
Heather Watson (front) and Andy Murray (left) for Great Britain in action during the mixed doubles match between Great Britain and Germany in Session 11 on Day 6 of the Hopman Cup at the Perth Arenaon January 8, 2016. Tony McDonough / EPA