Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 30/6/16 Germany's Sabine Lisicki in action against Australia's Samantha Stosur REUTERS/Paul Childs 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 30/6/16 Germany's Sabine Lisicki during her match against Australia's Samantha Stosur REUTERS/Paul Childs 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 30/6/16 Germany's Sabine Lisicki in action against Australia's Samantha Stosur REUTERS/Paul Childs 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 30/6/16 Germany's Sabine Lisicki in action against Australia's Samantha Stosur REUTERS/Paul Childs 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki during her match against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 USA's Shelby Rogers is reflected in the commentary box window during her rmatch against Germany's Sabine Lisicki REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 USA's Shelby Rogers is reflected in the commentary box window during her rmatch against Germany's Sabine Lisicki REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki in action against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki in action against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki celebrates after winning her match against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki celebrates after winning her match against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki celebrates after winning her match against USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Germany's Sabine Lisicki shakes hands with USA's Shelby Rogers after winning their match REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Spectators watch the match between Germany's Sabine Lisicki and USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Spectators watch the match between Germany's Sabine Lisicki and USA's Shelby Rogers REUTERS/Stefan Wermuth 

Britain Tennis - Wimbledon - All England Lawn Tennis & Croquet Club, Wimbledon, England - 27/6/16 Spectators watch the match between Germany's Sabine Lisicki and USA's Shelby Rogers REUTERS/Stefan Wermuth 

Tennis - Madrid Open - Carla Suarez Navarro of Spain v Sabine Lisicki of Germany - Madrid, Spain - 3/5/16 Suarez Navarro serves. REUTERS/Susana Vera 

Tennis - Madrid Open - Carla Suarez Navarro of Spain v Sabine Lisicki of Germany - Madrid, Spain - 3/5/16 Suarez Navarro returns the ball. REUTERS/Susana Vera 

Tennis - Madrid Open - Carla Suarez Navarro of Spain v Sabine Lisicki of Germany - Madrid, Spain - 3/5/16 Lisicki serves. REUTERS/Susana Vera 

Tennis - Madrid Open - Carla Suarez Navarro of Spain v Sabine Lisicki of Germany - Madrid, Spain - 3/5/16 Lisicki reacts. REUTERS/Susana Vera 

Czech Republic's Denisa Allertova reacts during her second round match against Germany's Sabine Lisicki at the Australian Open tennis tournament at Melbourne Park, Australia, January 21, 2016. REUTERS/Brandon Malone 

Czech Republic's Denisa Allertova (R) shakes hands with Germany's Sabine Lisicki after Allertova won their second round match at the Australian Open tennis tournament at Melbourne Park, Australia, January 21, 2016. REUTERS/Brandon Malone 

Czech Republic's Denisa Allertova celebrates after winning her second round match against Germany's Sabine Lisicki at the Australian Open tennis tournament at Melbourne Park, Australia, January 21, 2016. REUTERS/Brandon Malone 

Czech Republic's Denisa Allertova celebrates after winning her second round match against Germany's Sabine Lisicki at the Australian Open tennis tournament at Melbourne Park, Australia, January 21, 2016. REUTERS/Brandon Malone 

German comedian Otto Walkes, tennis star Sabine Lisicki and comedian Oliver Pocher (L-R) arrive on the red carpet for the Bambi 2015 media awards ceremony in Berlin, Germany November 12, 2015. The annual Bambi awards honour celebrities from the world of entertainment, literature, sports and politics. REUTERS/Stefanie Loos

Simona Halep of Romania celebrates after defeating Sabine Lisicki of Germany in their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Sabine Lisicki of Germany stretches a leg muscle during her fourth round match against Simona Halep of Romania at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania celebrates after defeating Sabine Lisicki of Germany in their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania celebrates after defeating Sabine Lisicki of Germany in their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania chases down a return to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania stretches a leg muscle after losing a point to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania chases down a return to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania serves to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania chases down a return to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania chases down a return to Sabine Lisicki of Germany during their fourth round match at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Simona Halep of Romania casts a shadow on the court during her fourth round match against Sabine Lisicki of Germany at the U.S. Open Championships tennis tournament in New York, September 7, 2015. REUTERS/Carlo Allegri

Timea Bacsinszky of Switzerland celebrates after winning her match against Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Timea Bacsinszky of Switzerland celebrates after winning her match against Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Timea Bacsinszky of Switzerland hits a shot during her match against Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Timea Bacsinszky of Switzerland slips during her match against Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Sabine Lisicki of Germany hits a shot during her match against Timea Bacsinszky of Switzerland at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Sabine Lisicki of Germany hits a shot during her match against Timea Bacsinszky of Switzerland at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Sabine Lisicki of Germany hits a shot during her match against Timea Bacsinszky of Switzerland at the Wimbledon Tennis Championships in London, July 4, 2015. REUTERS/Suzanne Plunkett

Spectators applaud Sabine Lisicki of Germany after she won her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany celebrates after winning her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany hits a shot during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany hits a shot during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Britain's Camilla, Duchess of Cornwall sits in the royal box on centre court to watch Christina McHale of the U.S.A. and Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Henry Browne 

Sabine Lisicki of Germany celebrates after winning the second set of her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany hits a shot during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany reacts during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany reacts during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany reacts during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Sabine Lisicki of Germany reacts during her match against Christina McHale of the U.S.A. at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth

Britain's Camilla, Duchess of Cornwall sits in the royal box on centre court to watch Christina McHale of the U.S.A. and Sabine Lisicki of Germany at the Wimbledon Tennis Championships in London, July 2, 2015. REUTERS/Stefan Wermuth