Nick Kyrgios is dealing with a wrist injury while Alex de Minaur continues to struggle with an abdominal tear that he picked up at the season-opening ATP Cup.
Roger Federer looked out for the count in a nailbiting fifth-set super tiebreaker against John Millman, but somehow found a way back.
Roger Federer scraped past John Millman 4-6, 7-6 (7/2), 6-4, 4-6, 7-6 (10/8) to stay alive in his quest for a 21st Grand Slam title.
Novak Djokovic, who played his first Japanese competition ever, dominated throughout the week, never losing a single set to claim the Japan Open trophy.
Two-time champion Novak Djokovic ended John Millman's fairytale US Open run on Wednesday, beating the 55th-ranked Australian in straight sets to book a semi-final clash with Kei Nishikori.
John Millman's joy was tinged with guilt after he stunned 20-time Grand Slam champion Roger Federer to reach the US Open quarter-finals.
The heat and humidity of the stadium hit Roger Federer badly during his US Open 2018 Round of 16 loss to John Millman.
Five-time champion Roger Federer crashed out of the US Open fourth round, beaten in four sets on Monday by 55th-ranked Australian John Millman.
Andy Murray beat Australia's John Millman 6-3, 7-5, 6-2 to enter Wimbledon fourth round.
The Croatian second seed, still without a title this year, was troubled by the 75th-ranked Millman before winning 6-3, 4-6, 6-3, helped by six aces in the final set.