The incident occurred as Sinner was leaving Arthur Ashe stadium for the locker room. A fan approached the seats Sinner had just vacated and reached for the bag slung over the 23-year-old's shoulder, attempting to unzip it. This happened while the world number one was signing autographs for other fans. Fortunately, a security guard noticed and intervened promptly.

A fan tries to open Sinner's bag on Arthur Ashe stadium, New York, USA, on the evening of 1/9. _Photo: Sports Mail_

As security stepped in, Sinner turned around, shaking his head and repeatedly asking what had happened. It remains unclear whether the US Open organizers will penalize the fan. Approximately 23,000 people attended Sinner's match against Bublik.

In the post-match press conference, Sinner joked that Bublik had gifted him a few free points in the one-sided, straight-sets match. "There are always days when I don't play my best and lose easily," the defending US Open champion said. "You never know what will happen. Tennis is very unpredictable."

Sinner reached the quarterfinals having dropped only one set and will face fellow countryman Lorenzo Musetti in the next round. This year, Sinner has reached three Grand Slam finals, losing only to Carlos Alcaraz at Roland Garros. Last year, he won the US Open, losing only two sets throughout the tournament.

"You can't control your opponent, you can only focus on yourself," Sinner added. "I try to do my best, and then let my performance on the court speak for itself. I'm happy with how I'm playing now, but that doesn't guarantee victory. It also depends on how your opponent plays."

Sinner during his match against Bublik in the fourth round of the US Open, on Arthur Ashe stadium, New York, USA, on the evening of 1/9. _Photo: Sports Mail_

According to the draw, Sinner could face Alcaraz again in the US Open final this year. However, he first has to overcome Felix Auger-Aliassime or Alex De Minaur, should he reach the semifinals.

Vy Anh