New York is known as the city that never sleeps – and so it has been at this year’s US Open.

A number of matches have started late and finished in the early hours, backing up the city’s reputation as a playground for the nocturnal.

But when some players – including men’s semi-finalists Ben Shelton and Alexander Zverev – are heading to bed as Manhattan commuters are waking up for work, it raises questions about fairness.

Three of top seed Zverev’s five matches over the past fortnight have finished past 1am.

“I’ve been to bed as late as 6:45am in the past week so I’m kind of a bit jet-lagged,” Zverev said.

“I feel like I’m playing the Australian Open in New York right now.”

Friday’s semi-final against Karen Khachanov – not before 15:00 local time/20:00 BST – will be the first time the German has played in the day at this year’s US Open.

By contrast, unseeded Khachanov has not been on court beyond midnight. He also has slightly longer to prepare after his quarter-final against Alexander Blockx finished shortly before 19:00 local time on Wednesday.

American eighth seed Shelton did not complete his last-eight victory over Carlos Alcaraz until 3:34am on Wednesday.

Shelton faces 11th seed Frances Tiafoe, who wrapped up his quarter-final about 19:00 on Tuesday after beating US compatriot Alex Michelsen in a five-set epic.

“The advantage of the opponent who has played earlier in the day will be big – they’ve had that full evening’s rest and a good night’s sleep,” Matt Little, who was Andy Murray’s long-time strength and conditioning coach, told BBC Sport.

“We can all relate to it – if you have one really bad night’s sleep, you have the knock-on effect of that for the coming days.”