A brazen US Open fan was caught red-handed trying to open and steal something from Jannik Sinner's bag on Monday night. br br The Italian had just secured his spot in the quarter-finals of the tournament in New York City and packed up his tennis gear before heading back to the locker room. br br Sinner, a four-time Grand Slam champion, was about to leave the court when he walked over to fans in the front row to hand one of them a towel. br br As he did so, Sinner then paused to take a selfie with another supporter. br br Sensing his opportunity, the daring fan can be seen leaning over and trying to try and pull the zip down on his bag. br br Fortunately, a security guard quickly noticed what was going on and swatted the fan's hands away before he got into Sinner's bag. br br Sinner quickly turned around to see what was going on, and the fan quickly pulled his hands back and looked embarrassed that he had been caught. br br It is not the first time during this year's US Open that a fan has gotten too carried away in trying to get items from a star player. br br A Polish millionaire businessman attracted fury last week when he stole a player's cap that was intended for a young fan. br br Piotr Szczerek was unmasked by internet sleuths after a viral video showed him swiping the memento intended for a child, known as Brock, by tennis star Kamil Majchrzak. br br He finally issued a groveling apology on Monday, saying in a lengthy statement he made 'a huge mistake' and revealed he has since given the hat back to Brock. br br Monday night's incident was an unsavory end to what had been a comfortable night for Sinner. br br Sinner overwhelmed the only player other than Carlos Alcaraz who has defeated him this season, routing Alexander Bublik 6-1, 6-1, 6-1 to return to the quarterfinals of the tournament he won last year. br br The top-seeded Sinner's victory took just 1 hour, 21 minutes, the second-shortest completed match in the tournament. A first-round victory for Tomas Machac was a minute shorter. br br 'At times I felt like today I was playing some great tennis, and I managed to break him very early, which then gave me the confidence to serve a little bit better and play from the back of the court a bit better,' Sinner said. br br 'It was a faster, or a fast match.' br br Sinner lost to Bublik in June in Halle, Germany, in a warm-up tournament before Wimbledon, but that was played on a grass court. Trying to beat the defending US Open champion on a hard court is an entirely different story. br br Sinner has won 25 straight Grand Slam matches on that surface, including the last two Australian Open titles, along with his first US Open trophy last year. br br He will face fellow Italian Lorenzo Musetti, the No. 10 seed, on Wednesday.