Following is reaction to Serena Williams' defeat by Australia's Ajla Tomljanovic at the US Open on Friday, likely to be the last match of the 23-times Grand Slam champion's career:
Former US 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."
Former world number one Billie Jean King
"Her incredible career made its mark on tennis history. And yet her greatest contributions may be yet to come. Thank you, @serenawilliams. Your journey continues."
Golf great Tiger Woods
"@serenawilliams you're literally the greatest on and off the court. Thank you for inspiring all of us to pursue our dreams. I love you little sis!!!!!!"
Australian player Ajla Tomljanovic
"I'm feeling really sorry just because I love Serena just as much as you guys do. What she's done for me, for the sport of tennis, is incredible.
"I never thought I'd have a chance to play her in her last match when I remember watching her in all those finals, so this is a surreal moment for me.
"I just thought she would beat me, so the pressure wasn't on me. Even to the last point, I knew she's in a position to win even when she's down 5-1. That's just who she is and she's the greatest of all time. Period."
American player Coco Gauff
"Serena, THANK YOU. It is because of you I believe in this dream. The impact you've had on me goes beyond any words that can be put together and for that I say thank you, thank you, thank you, GOAT!"
Former world number one Andy Roddick
"I love you @serenawilliams It's been the pleasure of a lifetime to watch you become what you have. Can't wait to see what you do next. Thank you my old friend."
American soccer player Alex Morgan
"Serena fighting until the last point, always. You've given so much to tennis, and so much to women's sports. Thank you @serenawilliams."
Australian player Daria Saville
"I feel so emotional realising that this was Serena's last match. I have a feeling she might reconsider? I don't know."
Former world number four James Blake
"Serena. Thank you for being you and the inspiration to so many men and women. I've never seen a more intense competitor and it was an honour to share a court with you and watch history. Simply the best. @serenawilliams."
American talk show host Oprah Winfrey
"25 years. Champion. Shero. Legend forever! @serenawilliams #USOpen."
Seven-times grand slam champion Mats Wilander
"Serena has meant so much for tennis and the world, but for America as well. I was watching the crowd and there are so many people here that have never been to a tennis match before... she has brought tennis to a completely new level and transcended the sport. We are going to remember Serena the person forever."
Olympic champion Allyson Felix
"I'm so grateful for @serenawilliams. What she has given this sport and us will never be lost on me. #ThankYouSerena."
Baseball hall of famer Derek Jeter
"It's been a joy watching greatness! Congrats Serena!"
Former world number seven Barbara Schett
"It's hard to believe the Serena Williams era is finished, probably the Venus Williams era is finished as well. It was just unbelievable how she held up such a big fight at the end."