Defending champion Iga Swiatek has been forced to withdraw from the Miami Open due to a rib injury.

The World No.1 said in a statement Wednesday that she'd been managing the injury since winning the Qatar TotalEnergies Open last month. The top seed in Miami, Swiatek was expected to play American Claire Liu in the second round on Thursday after receiving a first-round bye.

"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."

After losing in the semifinals of the BNP Paribas Open to eventual champion Elena Rybakina, Swiatek hinted at her physical concerns in an Instagram post. 

"I gave it all but Elena was a better player today," she wrote. "Unfortunately I'm feeling discomfort and pain in my ribs and it was challenging for me to compete at my highest level. Now, I just need to consult with my medical team and I will definitely use these next days to recover."

She said that the injury will also keep her out of Poland's Billie Jean King Cup Qualifier against Kazakhstan, to be played in Astana from April 14-15. 

"I will keep you updated about where I play next, because it depends on my process of recovering and the recommendation of my medical team," she said. "I have the best team behind me, we only need some time to deal with the injury. It's a truly difficult call to not play in Miami and BJKC, but health is the most important.

Swiatek said she first felt the injury toward the last few games against Sorana Cirstea in the quarterfinals of Indian Wells but wanted to complete the tournament. 

But Swiatek decided to take a more cautious approach to safeguard against her injury worsening in Miami. 

"I'm kind of aware if something hurts, it's usually going to be a problem in the future," Swiatek said in a press conference Wednesday at Hard Rock Stadium. "That's why I wanted to check it out as fast as possible. That's why I'm kind of taking a much more safe approach to that. That's why I'm pulling out." 

When asked about whether she had any concerns over rankings implications, Swiatek conceded she understand she'll lose points, "but it doesn't change anything in terms of my approach and my mentality.

 "I was also aware at the beginning of the season that it's going to be hard for me to defend all these points because it's not, like, these streaks, winning all these tournaments is like, looking logically and statistically, it's not like it's going to happen every year."

Swiatek did not lose a set in Miami last year, when she became the fifth woman to complete the Sunshine Double of winning Indian Wells and Miami back-to-back.

Swiatek will be replaced in this year's Miami Open draw by lucky loser Julia Grabher.