Novak Djokovic called on US Open organisers to find a solution to the humidity problems on Arthur Ashe Stadium after sweating his way through to the semi-finals. The Wimbledon champion, who next faces Kei Nishikori in a repeat of the 2014 semi-final which he lost, has struggled in the unusually extreme conditions in New York this year and was again in discomfort during a 6-3, 6-4, 6-4 victory over Australian John Millman that lasted nearly three hours on Wednesday.

Djokovic, for whom this was an 11th consecutive quarter-final victory, said: "I personally have never sweated as much as I have here. I have to take at least 10 shirts for every match. It's literally after two games you're soaking.