Serbia's Novak Djokovic looks on during a match against Argentina's Mariano Navone during the men's singles first round tennis match on day one of the US Open tennis tournament at the USTA Billie Jean King National Tennis Center in New York City on August 30, 2026. (Photo by CHARLY TRIBALLEAU / AFP via Getty Images)

Serbia's Novak Djokovic reacts during a match against Argentina's Mariano Navone during the men's singles first round tennis match on day one of the US Open tennis tournament at the USTA Billie Jean King National Tennis Center in New York City on August 30, 2026. (Photo by CHARLY TRIBALLEAU / AFP via Getty Images)

Serbia's Novak Djokovic wipes sweat off his forehead during a match against Argentina's Mariano Navone during the men's singles first round tennis match on day one of the US Open tennis tournament at the USTA Billie Jean King National Tennis Center in New York City on August 30, 2026. (Photo by CHARLY TRIBALLEAU / AFP via Getty Images)

Serbia's Novak Djokovic serves against Argentina's Mariano Navone during the men's singles first round tennis match on day one of the US Open tennis tournament at the USTA Billie Jean King National Tennis Center in New York City on August 30, 2026. (Photo by CHARLY TRIBALLEAU / AFP via Getty Images)

NEW YORK NEW YORK - AUGUST 30: Katie Boulter of Great Britain returns a shot against Carol Young Suh Lee of the United States during their Women's Singles First Round match on Day One of the 2026 US Open at USTA Billie Jean King National Tennis Center on August 30, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Julian Finney/Getty Images)

NEW YORK NEW YORK - AUGUST 30: Stefan Djokovic, son of Novak Djokovic, looks on at his father's match against Mariano Navone of Argentina during their Men's Singles First Round match on Day One of the 2026 US Open at USTA Billie Jean King National Tennis Center on August 30, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Julian Finney/Getty Images)

NEW YORK NEW YORK - AUGUST 30: Jelena Djokovic, wife of Novak Djokovic, looks on at his match against Mariano Navone of Argentina during their Men's Singles First Round match on Day One of the 2026 US Open at USTA Billie Jean King National Tennis Center on August 30, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Julian Finney/Getty Images)

NEW YORK NEW YORK - AUGUST 30: Ball kids use towels to dry raindrops on the court surface during the Men's Singles First Round match between Novak Djokovic of Serbia and Mariano Navone of Argentina on Day One of the 2026 US Open at USTA Billie Jean King National Tennis Center on August 30, 2026 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Julian Finney/Getty Images)