Defending US Open champion Jannik Sinner faces a two-front battle in New York — fitness concerns and the relentless Carlos Alcaraz. With their rivalry heating up, Sinner's title defence could hinge on his recovery as much as his tennis.

Spain’s Carlos Alcaraz has issued a big warning to his rival Jannik Sinner ahead of the U.S. Open. The fourth and final Grand Slam of the year will get underway on Sunday, where Sinner and Alcaraz will be the top two seeds in the men’s singles category.

Alcaraz praises Sinner's level but also warns the Italian that he will 'have a big target on his back' at the US Open.