Madison Keys of the US serves against Daria Gavrilova of Australia during their match of the 2016 Fed Cup tennis tournament World Group playoff between Australia and the United States at Pat Rafter Arena in Brisbane, Australia, 16 April 2016. EPA/DAVID KAPERNICK

Paula Kania of Poland returns the ball to Hsu Ching-Wen of Chinese Taipei during the Fed Cup World Group II match between Poland and Chinese Taipei in Inowroclaw, Poland, 16 April 2016. EPA/Tytus Zmijewski

Andrea Petkovic of Germany in action against Simona Halep of Romania during the Fed Cup World Group Play-off tennis match Romania vs Germany in Cluj city, 450Km north-west from Bucharest, Romania, 16 April 2016. EPA/ROBERT GHEMENT

French supporters and fans during the Fed Cup Tennis World Group semi-final tie between France and the Netherlands at Loire Arena in Trelaze, France, 16 April 2016. EPA/EDDY LEMAISTRE

Angelique Kerber of Germany in action against Romania’s Irina Begu during the Fed Cup World Group Play-off tennis match Romania vs Germany in Cluj city, 450Km north-west from Bucharest, Romania, 16 April 2016. EPA/ROBERT GHEMENT