Andy Murray has been coaching Novak Djokovic at the Australian Open this month and has been left surprised by one aspect of the Serb's behavior away from the court.

The recently retired Scot says his new charge is undoubtedly the greatest tennis player of all time, but has struggled to stay motivated since winning his first Olympic gold medal last year.

After dropping his opening set at the Australian Open to Nishesh Basavareddy, Noavk Djokovic eventually asserted himself for a victory to begin his bid for an 11th championship at Melbourne Park and a record 25th major title overall.