2015 champion Novak Djokovic booked a spot in the semi-final of the US Open last night, after battling his way past John Millman.

The 31-year-old Djokovic earned a 6-3, 6-4, 6-4 victory over the Australian World number 55 Millman.

The Serb, twice champion at Flushing Meadows, has now won all 11 of his quarter-final matches in New York.

Djokovic goes on to play Japan’s Kei Nishikori in the last four on Friday.

Djokovic missed last year’s tournament with an elbow injury …….but has now reached at least the semi-finals in every appearance at flushing meadows since 2007.

Kei Nishikori overcame seventh seed Marin Cilic in a grueling five-set match to reach the last four.

Nishikori took the contest 2-6, 6-4, 7-6, 4-6, 6-4 in four hours.