NUEVA YORK - 5 de septiembre de 2016: La campeona de Grand Slam Serena Williams de Estados Unidos en acción durante su cuarto partido en el US Open 2016 en el Billie Jean King National Tennis Center en Nueva York - Foto e imagen de stock

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - AUGUST 30, 2016: Grand Slam champion Serena Williams in action during first round match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States celebrates victory after her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - AUGUST 30, 2016: Grand Slam champion Serena Williams in action during first round match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 2, 2018: 23-time Grand Slam champion Serena Williams in action during her 2018 US Open round of 16 match at Billie Jean King National Tennis Center

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - AUGUST 29 Sixteen times Grand Slam champion Serena Williams during second round match at US Open 2013 against Galina Voskoboyeva at Billie Jean King National Tennis Center on August 27, 2013 in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 6, 2015: Twenty one times Grand Slam champion Serena Williams in action during her round four match at US Open 2015 at National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - AUGUST 30, 2016: Grand Slam champion Serena Williams in action during first round match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

FLUSHING, NY - AUGUST 29 Sixteen times Grand Slam champion Serena Williams during her first round doubles match with teammate Venus Williams at US Open 2013 at Billie Jean King National Tennis Center on August 29, 2013 in Flushing, NY

NEW YORK - SEPTEMBER 1, 2019: Grand Slam champion Serena Williams in action during her 2019 US Open round of 16 match at Billie Jean King National Tennis Center

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 6, 2018: 23-time Grand Slam champion Serena Williams in action during her 2018 US Open semi-final match at Billie Jean King National Tennis Center

NEW YORK - SEPTEMBER 5, 2016: Grand Slam champion Serena Williams of United States in action during her round four match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 3, 2016: Grand Slam champion Serena Williams of United States in action during her round three match at US Open 2016 at Billie Jean King National Tennis Center in New York

NEW YORK - SEPTEMBER 6, 2018: 23-time Grand Slam champion Serena Williams in action during her 2018 US Open semi-final match at Billie Jean King National Tennis Center