The latest chapter of the Jannik Sinner-Carlos Alcaraz rivalry took a stunning turn on Monday when world No. 1 Sinner retired in the first set of the Cincinnati Open final due to an unspecified health issue.

No one will be getting an early glimpse at the men’s world No.1 singles player in Flushing this year, nor an 11-time Grand Slam doubles champion.

It leaves Sinner battling to recover in time for the US Open singles, which gets underway this weekend. He is the defending champion, having beaten Taylor Fritz in last year's final. He will be desperate to retain his crown but will need to be in top condition in order to stand the best chance of success.

Nathan, a co-founder of the sports website Defector Media, has published “ Changeover: A Young Rivalry and a New Era of Men’s Tennis ” with Gallery Books. He spent the 2024 season squarely focused on Sinner and Alcaraz, in which they split the four majors and accelerated their ascension into a tennis stratosphere of their own creation.

Jannik defeated Terence Atmane in the semi-final in Ohio, celebrating his 200th ATP hard-court win and becoming the eighth-youngest player to achieve that in the Open era, standing right behind Rafael Nadal.

The No. 1-ranked Sinner, the defending champion in singles at Flushing Meadows, was supposed to compete in mixed doubles with Katerina Siniakova.