—Steffi and Venus are well-matched: speedy, leggy, a little haughty, wielding strong serves and harsh forehands that they hit late, and which rely on athleticism rather than sparkling technique.

It is easy to understand why both Sampras and Seles are Djokovic’s tennis inspirations. Sampras is a 14-time Grand Slam champion: a player widely considered to be the greatest of his generation and an ...