“I want to be number 1 in the world”. With these words, uttered just a month ago, Carlos Alcaraz almost seemed to be tempting fate in the aftermath of his Wimbledon loss to Jannik Sinner. At the time, the Italian, freshly triumphant at the Championships, seemed to have firmly in hand at the top of the ATP ranking. Then came Cincinnati. The final lost by Sinner to the Spaniard of all people put everything back on the table, opening up scenarios that only a few weeks ago seemed improbable. The South Tyrolean was defending the title he won in 2024, while Alcaraz had nothing to lose after last year's untimely exit: result, a leap forward in the rankings for the Spaniard and many points burned for Jannik. The same dynamic will be repeated at the U.S. Open, starting Sunday in New York: Sinner is called upon to defend his 2024 success, while Alcaraz can only gain. For the Italian, the situation is clear: in order to play it safe, he needs to win again. A lost final against Carlos would mean overtaking, but even in the event of an identical result achieved by the two (e.g., elimination in the quarters or semifinals), primacy would pass into the hands of the Spaniard. Making matters more delicate is the physical unknown. The crisis suffered in the final in Cincinnati has left some doubt about the condition of Sinner, who has given up the mixed doubles precisely to preserve energy for the tournament. September thus opens with a high-tension duel: at the US Open there is not only a title at stake, but also the primacy in world tennis.