Alexander Zverev
NEW YORK, NEW YORK - Alexander Zverev of Germany reacts against Jannik Sinner of Italy during their Men's Singles Fourth Round match on Day Eight of the 2023 US Open at the USTA Billie Jean King National Tennis Center Al Bello/Getty Images

German professional tennis player Alexander Zverev is no stranger to hearing derogatory remarks, but one fan who was watching when he played Jannik Sinner of Italy in the 2023 U.S. Open went a bit too far.

The 26-year-old was serving in the fourth set against the No. 6 when he suddenly approached chair umpire James Keothavong and pointed to a fan seated behind the official, the Associated Press reported.

"He just said the most famous Hitler phrase there is in this world," Zverev told Keothavong. "It's not acceptable."

Keothavong would then proceed to ask the fan to identify himself while at the same time requesting spectators to be more respectful to the players.

The said fan would later be identified and escorted out by security.

"A disparaging remark was directed toward Alexander Zverev," U.S. Tennis Association spokesman Chris Widmaier said, "The fan was identified and escorted from the stadium."

Zverev admitted that fans making derogatory remarks are nothing new to him and said he loves it when fans get involved. But of course, there are limitations.

"I think he was getting involved in the match for a long time, though. I don't mind it, I love when fans are loud, I love when fans are emotional. But I think me being German and not really proud of that history, it's not really a great thing to do and I think him sitting in one of the front rows, I think a lot of people heard it. So if I just don't react, I think it's bad from my side," Zverev stated.

Zverev went on to lose that set. The German netter, however, recovered in time in the fifth set to advance. He is set to face Carlos Alcaraz next in the quarterfinals.