India, May 25 -- "OMG," wrote Matteo Arnaldi with a fluorescent marker on the camera lens, in the post-match ritual reserved for the winner of a tour tennis match. Arnaldi had just won the biggest match of his career, beating 24-time Grand Slam champion Novak Djokovic in the second round of the Madrid Masters.

This was Djokovic a few weeks short of his 38th birthday. A Djokovic who had not won a title in the season, one who was seemingly fading due to the march of time.

But this was also a Djokovic whose aura transcends sport. He may be ageing, playing without a coach, and struggling for form - by his own exalted standard. But he is also one who can't be taken lightly.

In the current era of men's tennis, Jannik Sinner and Carlos Alcara...