Nick Kyrgios withdrew from the Sydney Tennis Classic after testing positive for Coronavirus.
The American was hoping to make his debut in Melbourne next week.
King of clay praises American serve-and-volley specialist as a unique threat to ATP Tour.
But why was the Serb out in public in the 16th, 17th and 18th?
Two-time Australian Open champion inspired by a dynamic veteran.
Former world No. 1 will debut in Sydney.
John Isner issues strong support of world No. 1.
