MIAMI GARDENS, Fla. — Defending champion Iga Swiatek withdrew from the Miami Open on Wednesday because of a rib injury that she is hoping will heal during a break from competition.

The No. 1-ranked Swiatek, a 21-year-old from Poland, also will sit out her country's Billie Jean King Cup qualifier matches against Kazakhstan on April 13-14.

"I wanted to wait 'til the last minute" to decide whether to play in Miami," Swiatek said at a news conference at the site of the hard-court tournament that began Tuesday.

"We were kind of checking if this is the kind of injury you can still play with or this is kind when you can get things worse. So I think the smart move for me is to pull out of this tournament because I want to rest and take care of it properly." She was supposed to face Claire Liu in the second round on Thursday.

As a seeded player, three-time Grand Slam champion Swiatek received a first-round bye at an event she won a year ago during a 37-match unbeaten run that was the longest in women's tennis in a quarter of a century.

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

Swiatek said after a 6-2, 6-2 loss to eventual champion Elena Rybakina in the BNP Paribas Open semifinals Friday that her rib was bothering her. She explained in Miami that the problem first surfaced late in her quarterfinal victory against Sorana Cirstea a day earlier in California.

"Basically, it's not like it happened in one minute or one second. It's not, like, a serious thing, because we caught it ... pretty early. So I felt like it was a process," Swiatek said Wednesday.

"At first with these minor things, your body doesn't feel anything." She said the issue was a problem "in certain movements," including a "little bit when I served," but Swiatek also said she's not too worried about how long she will be sidelined.

The next Grand Slam tournament is the French Open, which Swiatek won last year for the second time. Play begins in Paris on May 28.

Instead of playing Swiatek, Liu will go up against 94th-ranked Julia Grabher, who lost in qualifying but now gets to move into the draw.

Liu advanced Tuesday when her first-round opponent, Katerina Siniakova, stopped playing in the second set because of a hurt wrist. Siniakova also pulled out of the doubles event with Barbora Krejcikova; the Czech duo has won the past four Grand Slam tournaments they've entered together, and seven major doubles titles overall.

AP