Novak Djokovic of Serbia celebrates after defeating Rafael Nadal of Spain during their men's quarter-final match during the French Open tennis tournament at the Roland Garros stadium in Paris, France, June 3, 2015. [Photo/Agencies]

 "At the end of the day, he's human. I understand that people are questioning his game. But if you need a reminder of who he is, you just look at his career stats and grand slams that he won."

Djokovic's next test will be against a player who also boasts a 15-0 record on red dirt this year.

Murray's triumph over Ferrer ended a miserable day for the Spaniards, who will not feature in the last four here for the first time since 2009.