NEW YORK, NEW YORK – SEPTEMBER 10: Novak Djokovic of Serbia reacts as he plays against Alexander Zverev of Germany during their Men’s Singles semifinal match on Day Twelve of the 2021 US Open at the USTA Billie Jean King National Tennis Center on September 10, 2021 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Sarah Stier/Getty Images)
