Defending champion arrives at Flushing Meadows in poor form and with a host of challengers looking to usurp her

Under any normal circumstances Aryna Sabalenka would not have lost her third-round match at the Cincinnati Open last week. For all of her unforced errors, indecisiveness and the obvious tension surrounding her tennis, the world No 1 had led the unheralded Sára Bejlek 5-1 in the first set tie-break and then 4-1 in set two. She gave herself more than enough chances to close out a comfortable win.

Instead Sabalenka returns to New York trying to find a path through her greatest crisis since she first reached No 1 in the rankings more than three years ago. That straight-sets loss in Cincinnati extended a mediocre 17-7 record dating back to the beginning of April during which she has not reached a final. She has just one more chance to turn her fortunes around as she tries to claim her first grand slam title of the year at the US Open, the tournament she has won on the last two occasions.

With one semi-final in her last seven tournaments, the coming months will define the next stage of her career

Towards the end of a messy first set tie-break late on Wednesday, Aryna Sabalenka wildly sprayed another painfully nervous backhand before slamming her racket to the ground. As the racket connected with the acrylic floor, its vibration dampener detached from the strings and rolled off in the direction of the broadcast camera pit by the side of the court.

With the diminutive 20-year‑old Czech player Sara Bejlek leading Sabalenka 6-5 in the tie-break, this slapstick sequence forced play to pause while the Belarusian and a couple of volunteers comically searched for the missing vibration damper underneath the cameras until she gave up and retrieved a new one. A few minutes later, Sabalenka trailed by a set.