Defending US Open champion Dominic Thiem will miss this year's tournament and the rest of the 2021 season with a wrist injury.
The Austrian, 27, withdrew from Wimbledon and has not played since the Mallorca Open in June, where he sustained the injury.
He said it was a "tough decision" and is "disappointed" to not be able to defend his title in New York.
The US Open begins on Monday, 30 August.
The world number six broke the news on Twitter and said: "I've been following the medical advice - my recovery was going really well but last week I hit a ball in training and started to feel some pain again.