The US Open has been overshadowed by a growing list of withdrawals, with the tournament facing the kind of disruption that has reignited debate over the demands of the modern calendar.

A total of 23 players are absent from this year’s entry list, and several of the ATP Tour’s leading names have chosen not to take part in New York. Jannik Sinner is the most notable withdrawal after an injury to his knee, while Joao Fonseca, Jack Draper, Marin Cilic and Casper Ruud are also among those missing from the event.

Thanasi Kokkinaki became the 14th man to pull out, prompting an official response from the ATP Tour as concern around the scale of the withdrawals has intensified.

In a statement to Sky Sports Tennis, the governing body said: “Professional tennis is physically demanding and injuries are rarely attributable to a single factor.

“Every case has its own context, shaped by factors including a player’s medical and injury history, match and training load, travel, surface transitions, recovery and playing conditions.”

Patrick Mouratoglou has offered a different explanation. The coach said he believes two issues are central to the rise in injuries this season. Speaking to Sky Sports Tennis, he said: “There are many more injuries and this year particularly. I think the two major problems are the change of balls and the body having to adapt not only to the surfaces, not only to the weather conditions, but also the balls and some are heavier, some are softer.

“I think this is harming the body. The second one I can think of is the fact that now the surfaces are much slower than 20 years ago, which pushes the player to play longer rallies, hit the ball harder.

“To hit winners now you have to really go for it and, if you look at the new generation, all of them are hitting the ball extremely hard – and most of them are injured.”

Complaints about balls have surfaced on both tours this season, with Emma Raducanu and Daniil Medvedev among those to raise concerns. The US Open remains the only Grand Slam where the men and women use different balls, with the women playing with the more traditional version used across much of the North American hard-court swing and the men using a heavier ball at Flushing Meadows.

For players, the issue remains consistency across the full 10-month season.

Novak Djokovic suffered another difficult setback at the US Open, exiting in the opening round after a five-set loss to Mariano Navone.

The Serbian was again hindered by health issues in New York’s humid conditions, and the defeat marked a third straight loss for him. That sequence began with his defeat to Jannik Sinner in the Wimbledon semi final, continued with an opening-match loss at the Cincinnati Open, and now includes the US Open setback.

The early exit drew a strong response from Brad Gilbert, who argued that Djokovic may need to alter his schedule. Speaking on The Big T Podcast, the former coach of Coco Gauff and Andy Murray said: “I also think the big change, if I was talking to Novak, he’s playing the same schedule that he was playing three years ago, five years ago, when he was dominating.

“I feel like he’s undercooked now. He needs to play more matches and he needs more reps. It’s weird to say that.” “The reason why I say that is because it’s not about winning Cincy, but it’s about getting into match fit form, getting into match shape and when you’re not playing that many matches it’s not that easy just to turn it on.

“And at 39, the biggest challenge is, I’m sure what Federer went through, what Rafa went through, [Andy] Murray and a lot of guys, great champions. If you feel like you can’t win the tournament, that’s probably when father time has beaten you.

“I’m sure he feels like the opportunity was, especially with [Jannik] Sinner out, he missed the opportunity at the French, he still feels like he can win it, he probably hasn’t come to that resolution.

“But I just feel like he’s undercooked in matches and there’s definitely something going on and he revealed this sickness that he needs to figure out, but he needs to I feel like get back to winning a few matches.

“I know you don’t think he needs to, but that’s the belief in the locker room that he needs to show guys. If you lose to guys like this, everybody’s going to start thinking you’re beatable.”

A recent development may indicate Djokovic is prepared to heed that advice. The 24-time Grand Slam champion has been listed for the China Open later this month, which would be his first appearance at the ATP 500 event since the 2015 season.

Carlos Alcaraz began his US Open campaign with a straight-sets win over Roman Safiullin on the Grand Slam’s second day, marking a successful return to competition after a wrist injury forced him out since April’s Barcelona Open.

The Spaniard needed only one match to remind the field why he remains among the favourites for the title, especially with Novak Djokovic already gone and Jannik Sinner absent from the draw. His reward is a second-round meeting with Jaime Faria, while the road ahead could become far more demanding if he keeps progressing.

Not everyone is fully convinced the tournament will unfold smoothly for him. Greg Rusedski remains wary of Alcaraz’s condition, but several other pundits have pointed to the ease of his New York start as a positive sign.

On Sky Sports’ US Open coverage, Martina Navratilova described the timing of Alcaraz’s comeback as a “perfect situation” after his five-month absence. She said the match did not overtax him and argued that the best-of-five format can work in his favour, provided his arm stays healthy.

“He was pushed but not too much, he is going to get better and the three out of five format really helps him here, as long as the arm doesn’t get hurt,” continued Navratilova.

“If it holds up, three out of five is great because it gives him a little cushion. He doesn’t have to stress about getting broken and the other guy has to play well for three of five sets and that gives him a chance to get into the tournament.

“You could see during the match that he became more comfortable and at the end he hit that unbelievable drop shot volley inside out. He is all back!”

Navratilova also recalled speaking to him backstage after he had secured his place in round two.

“I bumped into him in the hallway,” she added. “He is so happy to be back and see everybody, that’s what he said. You can see it. He is a competitor and a kid at heart.

“He is playing a sport for a living and he is phenomenal at it and what is not to love? It is so great to have him back.”

If Alcaraz gets through Faria, he would next face either James Duckworth or Wu Yibing. A possible fourth-round match against Alexander Bublik or Tommy Paul would provide a much sterner examination of his limited match practice.