Serena Williams withdrew from the WTA and ATP Masters Miami Open on Saturday with a left knee injury. The 23-time Grand Slam champion's withdrawal comes a day after she beat Sweden's Rebecca Peterson in three sets to reach the third round.

"I am disappointed to withdraw from the Miami Open due to a left knee injury," said Williams, an eight-time winner in Miami who has completed just seven matches this year. The 37-year-old superstar, now ranked 10th in the world, appeared to be moving freely against Peterson, but said she needed to play better than she did in a 6-3, 1-6, 6-1 win.