Serena Williams of the USA gestures after being defeated by Ajla Tomljanovic. | JASON SZENES
FORMER U.S. FIRST LADY MICHELLE OBAMA "Congrats on an amazing career, @SerenaWilliams! How lucky were we to be able to watch a young girl from Compton grow up to become one of the greatest athletes of all time. I'm proud of you, my friend -- and I can't wait to see the lives you continue to transform with your talents."