World number two Andy Murray has become the latest high-profile player to withdraw from the US Open, after failing to recover sufficiently from his ongoing hip problem.
The US Open champion in 2012, Murray has not played since losing to Sam Querrey in the quarter-finals of Wimbledon.
He was clearly hampered by his hip injury in that match and remains short of full fitness despite a period of rest.
At a news conference in New York on Saturday, Murray said: "I did pretty much everything I could to get myself ready here, took a number of weeks off after Wimbledon, obviously spoke to a lot of hip specialists, tried resting and rehabbing to try and get myself ready.
"It was actually progressing okay the last few days, but it's too sore for me to win the tournament and ultimately that's what I was here to try and do.
"So, unfortunately, I won't be playing."
Murray's withdrawal from the men's singles adds to a hefty list of absentees that includes defending champion Stan Wawrinka, Novak Djokovic, Milos Raonic and Kei Nishikori.
Alexander Zverev, the winner of two recent Masters 1000 titles, is now the highest-ranked player in the bottom half of the draw, with Roger Federer and world number one Rafael Nadal both in the top half.
Asked if he hopes to play again this season, Murray added: "I'll definitely make a decision on that in the next few days.
"I'll need to make the correct decision and really think it through these next couple of days with my team.
"I certainly wouldn't have been hurting myself more by trying to play. It was more a question of whether it would settle down in time. Obviously, I kind of ran out of time.
"I have never had to take time off because of my hip before, so we were hoping that by taking a few weeks off and resting and rehabbing and really reducing the load that I was putting through it, I would be okay by the time the US Open came around, but unfortunately that's not been the case."