Novak Djokovic of Serbia returns to Sam Querrey of the US in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA

Sam Querrey of the US returns to Novak Djokovic of Serbia in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA

Novak Djokovic of Serbia returns to Sam Querrey of the US in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA

Sam Querrey of the US serves against Novak Djokovic of Serbia in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA

Novak Djokovic of Serbia returns to Sam Querrey of the US in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA

Sam Querrey of the USA celebrates his win over Novak Djokovic of Serbia in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club in London, Britain, 02 July 2016. EPA/PETER KLAUNZER

Novak Djokovic of Serbia walks off court following his defeat by Sam Querrey of the US in their third round match during the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 02 July 2016. EPA/FACUNDO ARRIZABALAGA