Naomi Osaka upsets Serena Williams in controversial US Open final

Naomi Osaka, of Japan, reacts after breaking the serve of Serena Williams during the women's final of the U.S. Open tennis tournament, Saturday, September 8, 2018, in New York.

Naomi Osaka, of Japan, holds the trophy after defeating Serena Williams in the women's final of the U.S. Open tennis tournament, Saturday, September 8 in New York.

Alize Cornet (FRA) plays her first round at the 2018 US Open at Billie Jean National Tennis Center in New York City, NY, USA, on August 28, 2018. Photo by Corinne Dubreuil/Abaca/Sipa USA(Sipa via AP Images)

PARIS, FRANCE - MAY 28: Rafael Nadal of Spain plays a backhand during his mens singles first round match against Simone Bolelli of Italy during day two of the 2018 French Open at Roland Garros on May 28, 2018 in Paris, France. (Photo by Clive Brunskill/Getty Images)

Looking Back on the Scottish Open, and Wimbledon _00004101.jpg

Russia's Maria Sharapova during her semi final round match at the French Tennis Open at Roland-Garros arena in Paris, France on June 6, 2013. Photo by Corinne Dubreuil/ABACAPRESS.COM

SEP 1989: YANNICK NOAH OF FRANCE PERFORMS A RUNNING FOREHAND DURING A MATCH AT THE 1989 US OPEN PLAYED AT FLUSHING MEADOWS IN NEW YORK.

PARIS, FRANCE - JUNE 07: Novak Djokovic of Serbia serves in the Men's Singles Final against Stanislas Wawrinka of Switzerland on day fifteen of the 2015 French Open at Roland Garros on June 7, 2015 in Paris, France. (Photo by Julian Finney/Getty Images)

NEW YORK, NY - SEPTEMBER 10: Rafael Nadal of Spain bites the championship trophy during the trophy ceremony after their Men's Singles Finals match on Day Fourteen of the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 10, 2017 in the Flushing neighborhood of the Queens borough of New York City. Rafael Nadal defeated Kevin Anderson in the third set with a score of 6-3, 6-3, 6-4. (Photo by Clive Brunskill/Getty Images)

NEW YORK, NY - SEPTEMBER 09: Sloane Stephens of the United States poses with the championship trophy during the trophy presentation after the Women's Singles finals match on Day Thirteen of the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2017 in the Flushing neighborhood of the Queens borough of New York City. Sloane Stephens defeated Madison Keys in the second set with a score of 6-3, 6-0. (Photo by Elsa/Getty Images)

NEW YORK, NEW YORK - SEPTEMBER 03: Denis Shapovalov of Canada reacts during his fourth round match against Pablo Carreno Busta of Spain on Day Seven of the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 3, 2017 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Richard Heathcote/Getty Images)

NEW YORK, NY - SEPTEMBER 09: Sloane Stephens of the United States poses with the championship trophy during the trophy presentation after the Women's Singles finals match on Day Thirteen of the 2017 US Open at the USTA Billie Jean King National Tennis Center on September 9, 2017 in the Flushing neighborhood of the Queens borough of New York City. Sloane Stephens defeated Madison Keys in the second set with a score of 6-3, 6-0. (Photo by Elsa/Getty Images)