Watching Djokovic has become a live-action demonstration of a tennis player figuring out his limits from match to match and week to week.

Novak Djokovic is struggling for form, losing his last three games to inspire a wave of fresh questions over the 37-year-old's future in tennis.

Novak traveled to the USA and wished for a better run in Indian Wells. However, he fell in the second round to Botic van de Zandschulp, playing poor tennis in sets one and three and suffering his third straight defeat. Djokovic and Murray will work hard in the upcoming days in Miami.