March 16 (UPI) -- Just hours before he was to take the court in the semifinals at the BNP Paribas Open in Indian Wells, California, Rafael Nadal was forced to withdraw due to a knee injury.
"I warm up today in the morning, and I felt that my knee was not enough good to compete at the level that I need to compete," an upset Nadal said.
Nadal was to face rival Roger Federer in the semis.
Nadal's right knee flared up while he was taking on Karen Khachanov in Friday's quarterfinals. He defeated Khachanov 7-6 (2), 7-6 (2) to set up the meeting with longtime rival Federer.
Saturday would have been the 39th meeting between Nadal and Federer, with Nadal leading the all-time series 23-15.
Nadal has defeated Federer in nine of 12 Grand Slam matchups.
"It's tough for me to accept all these things that I'm going through in my career. Sometimes I feel sad because I'm in a disadvantage to all my opponents," Nadal said in a statement Saturday.
Knee issues are nothing new for Nadal, as his 2018 season ended early after the U.S. Open in September.
It was just two sets into his semifinal match against Juan Martin del Potro that he had to stop due to his knee acting up.
Nadal stated that he will be back, with plans of taking time off and returning to the court in mid-April for the Monte-Carlo Masters.
"I don't have doubts today that I will be ready for Monte Carlo," Nadal said.