New York: Former first lady Michelle Obama hailed Serena Williams as “the greatest” on Friday as the tennis superstar headed into retirement. Williams, the winner of 23 Grand Slam titles, played what was almost certainly the last match of her 27-year career at the US Open when she slipped to a three-set defeat to Ajla Tomljanovic. Michelle Obama hailed Serena for her rise to super-stardom from the tough Californian neighborhood of Compton to sporting and cultural icon. “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,” tweeted Obama. “I´m proud of you, my friend and I can´t wait to see the lives you continue to transform with your talents.” Television and entrepreneur Oprah Winfrey described Williams as a “Shero. Legend forever” while US sprinter Allyson Felix said her achievements “will never be lost on me”.