Roger Federer of Switzerland waves goodbye to the audience after the men's singles fourth round match against John Millman of Australia at the 2018 US Open in New York, the United States, Sept. 3, 2018. Millman won 3-1. (Xinhua/Wang Ying)

NEW YORK, Sept. 4 (Xinhua) -- 20-time Grand Slam singles champion Roger Federer was stunned by unheralded Australian John Millman 3-6, 7-5, 7-6 (7), 7-6 (3) in the fourth round at the US Open on Tuesday.

The match, starting on Monday and ending well past midnight, saw the tennis legend fall to the 55th ranked Millman.

Millman will take on 13-time Grand Slam winner Novak Djokovic in the quarterfinals after the 6th seeded Serbian sailed past Joao Sousa of Portugal 6-3, 6-4, 6-3.