When watching tennis, particularly in the early stages of a grand-slam competition, I pretend that I do not know the identity of the protagonists. Instead, I watch the warm-up and early exchanges and seek to detect who is the superior player not on their ranking or reputation, but in the way they play, move and compete.

The warm-up is never, and I mean never, informative. Every player who makes it to the opening rounds of the grand-slams hits with speed and felicity, moves with a certain degree of fluency, and rarely makes unforced errors. I defy any expert to make significant pronouncements on the relative quality of players from the few minutes of sparring.

Djokovic eased past Kohlschreiber on Centre Court, winning 6-3, 7-5, 6-3 TIMES PHOTOGRAPHER MARC ASPLAND

It is only once the match starts that clues start to