Elena Rybakina is one of the most promising players on the tour, but the world No.4 is also proving to be one of the most vulnerable.

Fitness has been a struggle for the Russian-born who plays for Kazakhstan, and her withdrawal from the US Open on Thursday has raised some eyebrows. There have been murmurs that all may not be well with her, and not just physically.

Rybakina, seeded fourth at the last grand slam of the year, had won her first-round match 6-1, 7-6 (7-1) against Destanee Aiava. She was scheduled to play Jessika Ponchet on Thursday.

This is the eighth time she has withdrawn from a tournament due to illness or fatigue in 2024.

It may be noted that she had split with long-time coach Stefano Vukov just before the US Open started.

“Unfortunately, I have to withdraw from my match today due to my injuries,” said Rybakina in a statement on social media. “I did not want to finish the last grand slam of the year this way but I have to listen to my body, and I hope I can close out the remainder of the year strong.

“Thank you to all the fans who have and continue to support me, and I wish the remaining players good luck.”

She, however, did not specify the injury.

Her decision to withdraw from the US Open made former player and now commentator Rennae Stubbs voice her concern.

“There’s something obviously going on here. I don’t want to speculate. But this is a very unusual situation. Eight withdrawals this year… undisclosed injury now at US Open. I just think there’s something more going on here,” Stubbs told ESPN.

“This is not a normal situation. I’ve seen her over the last couple of days. She hasn’t looked great. I’ve seen her for years on the tour. I know what she looks like when she’s happy, when she’s healthy, when she’s playing well,” the former world No.1 in doubles said.

“When she’s playing well, on this surface, she’s one of if not the best player in the world.

“So what’s going on with her, I think it’s a lot more than we realise. This is terrible. It’s sad. She’s such a nice person. She’s so nice to be around all the time. We wish her well and hope she can find whatever she needs to.”

There had also been some concern after Rybakina’s appearance at a media conference after her first-round match at Flushing Meadows, where she was very guarded over the split with Vukov.

“Well, of course, it is different,” she had said, when asked how it felt to play a match without Vukov.

Rybakina had announced her parting with Vukov on social media on August 23. “Hello Everyone, after 5 years, Stefano and I are no longer working together,” she had posted on her Instagram stories.

“I thank him for his work on-court and wish him all the best for the future. Thank you all for your support.”

Rybakina had Vukov as coach throughout her rise up the WTA rankings, winning the 2022 Wimbledon and finishing runner-up at the 2023 Australian Open.

Mental health has been brought to the fore in world tennis in recent years, specially after Naomi Osaka, then the world No.2, shockingly withdrew from the 2021 French Open.

Dominic Thiem, too, had opened up on how he was mentally spent after winning the 2020 US Open.

Pat Cash, who won Wimbledon in 1987, wrote in his autobiography Uncovered about how he was hounded by depression, which even forced him to consider suicide.

After being stabbed by a deranged Steffi Graf fan at Hamburg in 1993, 19-year-old Monica Seles lost her No.1 ranking on the WTA charts and also found it difficult to deal with the incident physically and emotionally.

Jelena Dokic has also written about her physical, emotional and mental struggles in her autobiography Unbreakable.