Poland's tennis ace Iga Swiatek pulled out of the Miami Open tournament on Monday due to a rib injury.
The Pole was the defending champion at Miami and was expected to play American Claire Liu in the second round on Thursday after receiving a first-round bye.
She lost in the semifinals of Indian Wells to eventual champion Elena Rybakina but said that she was not able to play again with the injury.
Swiatek said she had initially hurt her rib by strong coughing after picking up an infection.
"You know that in and after Doha I was struggling with a strong infection," Swiatek said.
"I was allowed to play, but a strong episode of tough cough led to a rib injury. We were trying to handle it and continue to play as long as it was safe for me. We were analyzing the data in the last days and my doctor prepared my diagnosis.
"Unfortunately, I'm still feeling a lot of discomfort and pain and I can't compete."
Swiatek suggested the injury was not serious enough to keep her sidelined for long, although she did not indicate a timeline for her return.
With a strong lead over second-placed Aryna Sabalenka in the rankings, Swiatek's No. 1 status will not be immediately impacted by missing Miami.
"Of course I'm going to lose points for this tournament but it doesn't change anything in terms of my approach and my mentality," she said.
"I was also aware at the beginning of the season that it's going to be hard for me to defend all these points.
"Missing this tournament is not going to help, but on the other hand, as I said, you know injuries happen and I didn't have any injuries for two or three years.
"What's going to happen next? We'll see. Obviously it's going to depend on the recovery but for now it's not a horrible scenario."
Swiatek said in a statement that she would also miss Poland's upcoming match against Kazakhstan in the Billie Jean King Cup competition.
