US Open, Best Pictures: Day 6

NEW YORK, NY - AUGUST 30: Kei Nishikori of Japan meets Leonardo Mayer of Argentina after winning their men's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Matthew Stockman/Getty Images)

NEW YORK, NY - AUGUST 30: Petra Kvitova of the Czech Republic reacts against Aleksandra Krunic of Serbia during their women's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)

NEW YORK, NY - AUGUST 30: Flavia Pennetta of Italy celebrates match point to defeat Nicole Gibbs of the United States in women's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Streeter Lecka/Getty Images)

NEW YORK, NY - AUGUST 30: Jo-Wilfried Tsonga of France celebrates after defeating Pablo Carreno Busta of Spain in their men's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)

NEW YORK, NY - AUGUST 30: Serena Williams of the United States reacts against Varvara Lepchenko of the United States during their women's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Chris Trotman/Getty Images for USTA)

NEW YORK, NY - AUGUST 30: Philipp Kohlschreiber of Germany celebrates after defeating John Isner of the United States in their men's singles third round match on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Al Bello/Getty Images)

NEW YORK, NY - AUGUST 30: A fan wears a had adorned with US Open pins while watching play on Day Six of the 2014 US Open at the USTA Billie Jean King National Tennis Center on August 30, 2014 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Mike Stobe/Getty Images for USTA)