Jannik Sinner has withdrawn from the Mixed Doubles event at the US Open. The world No.1 was due to enter the revamped format with Czech star Katerina Siniakova after his initial partner, Emma Navarro, pulled out in favour of playing a WTA 500 event in Monterrey.

However, his place in the draw appeared in doubt following his Cincinnati Open final with Carlos Alcaraz on Monday. The 24-year-old looked desperately out of sorts as he trailed 5-0 in just 23 minutes, and sat with ice on head during changeovers. After the fifth game he called a medical timeout and head a lengthy discussion with his trainer.

In tears, Sinner then officially conceded the match. He apologised to the umpire and officials, and was heard saying that he "felt really bad" for the fans, raising his hands to them by way of apology.

Post-match, he said: "I'm super sorry to disappoint you. From yesterday I didn't feel great, I thought I would improve but it came up worse. I tried to come out, to make it at least a small match, but I couldn't handle more. I am very sorry for all of you."

The official US Open X account has now confirmed his decision, posting: "Mixed Doubles Update: Jannik Sinner has withdrawn from the Mixed Doubles event with an illness. The team of Siniakova/Sinner is replaced by Danielle Collins and Christian Harrison."

The event has already lost Paula Badosa and Tommy Paul, who had been due to play with Jack Draper and Jessica Pegula. The latter two have now teamed up together to play, while Jasmine Paolini and Lorenzo Musetti have moved into the draw.

Sinner's withdrawal is undoubtedly a blow to organisers, as the event is designed to attract supporters during US Open Fan Week. The 16 entrants comprise eight teams based on their joint rankings, with the other eight given wildcards.

Matches will be played on Arthur Ashe Stadium and Louis Armstrong Stadium, the two largest show courts at Flushing Meadows. However, the format has faced criticism from those who believe it is denying opportunities for genuine doubles players to compete.