NEW YORK, NY - AUGUST 29: Serena Williams of the United States celebrates victory following her women's singles second round match against Carina Witthoeft of Germany on Day Three of the 2018 US Open at the USTA Billie Jean King National Tennis Center on August 29, 2018 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Sarah Stier/Getty Images)