The 36-year-old athlete -- who was supposed to play a fourth-round match against Maria Sharapova on Monday -- pulled out of the tennis tournament due to a chest muscle injury, ESPN reports.
Serena announced her withdrawal during a news conference, telling reporters, "It's extremely disappointing."
"But also, I made a promise to myself and to my coach and to my team that if I'm not at least 60 percent or 50 percent, then I probably shouldn't play," she continued. "The fact that I physically can't serve at all is a good indication that maybe I should just go back to the drawing board and stay positive. And try to get better and not get it to a point where it could be a lot worse."
Following the news, Serena took to Instagram to thank her fans for their support.
"You always live to fight for another chance," she captioned a pic of herself on the court. "I've done a lot of fighting and this is just the beginning. Thank you a for the support. I love you."
Late last month, the tennis champ and her sister, Venus Williams, won a doubles match during the French Open, just one day after Serena won her first grand slam match 14 months after giving birth to her first child, baby girl Alexis Olympia, with husband Alexis Ohanian.
ET caught up with Serena back in March, where she revealed there's been a bit of mom guilt since returning to tennis.
"I've always wanted to be a mom but I never seemed to have time with my career," she said at the 14th Annual Desert Smash Celebrity Tennis Event in La Quinta, California. "I'm never a day without Olympia. She's my priority and everyday I need to be home with her. I don't wanna miss any moments with her."