A knee injury has forced Serena Williams to withdraw from the Wimbledon’s doubles tournament, the 23-time Grand Slam champion announced on Saturday.

Williams sustained the knee injury during her first-round singles loss to Maya Joint, putting the doubles match with her sister Venus in jeopardy.

“I’m heartbroken to have to withdraw from doubles,” Williams wrote in a message on Instagram. “Coming back to compete again has been a gift, and the opportunity to play alongside Venus once more meant the world to me. I did everything I could to be ready, but unfortunately my knee just isn’t ready to compete.

I’m especially grateful to tournament director, Jamie Baker, and the entire tournament team for giving me every opportunity to play here. Thank you to the fans for your incredible support and for making this comeback so meaningful…..All I can say is stay tuned to a city near you…

The photo of the syringes shows the fluid they drained from my knee after my singles match…yikes! The good news is my knee shouldn’t swell or collect that much fluid again. The bad news is that, as hard as I tried, I just wasn’t able to get it ready for doubles.”