British / Scottish tennis player Andy Murray (R), watched on by his coach, former French tennis player, Amelie Mauresmo, during his training session, in preparation for the Australian Open tennis tournament, in Melbourne, Australia, 15 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/DAVID CROSLING AUSTRALIA AND NEW ZEALAND OUT

Rafael Nadal of Spain during his training session in Melbourne, Australia, 15 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/DAVID CROSLING AUSTRALIA AND NEW ZEALAND OUT

A picture made available on 14 January 2015 shows Ana Ivanovic of Serbia in action during a practice session for the Australian Tennis Open at Hisense Arena in Melbourne, Australia, 13 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/JOE CASTRO AUSTRALIA AND NEW ZEALAND OUT

Swiss tennis player Roger Federer during his training session, in preparation for the Australian Open tennis tournament, in Melbourne, Australia, 15 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/DAVID CROSLING AUSTRALIA AND NEW ZEALAND OUT

Maria Sharapova (R) of Russia during her training session in Melbourne, Australia, 15 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/DAVID CROSLING AUSTRALIA AND NEW ZEALAND OUT

A picture made available on 14 January 2015 shows Novak Djokovic of Serbia in action during a practice session for the Australian Tennis Open at Rod Laver Arena in Melbourne, Australia, 13 January 2015. The Australian Open tennis tournament runs from 19 January until 01 February 2015. EPA/JOE CASTRO AUSTRALIA AND NEW ZEALAND OUT