Novak Djokovic’s stunning defeat to humble giant Reilly Opelka at Brisbane International

Novak Djokovic looked puzzled.

Djokovic is not someone who is accustomed to being puzzled.

When you have been on tour for over 20 years, played 1,346 matches at ATP level, won 24 grand slam singles titles and an Olympic gold, there are not all that many situations that you’ve not come across…