Former No. 1 Caroline Wozniacki to retire after 2020 Australian Open

On Friday, Former world No. 1 Caroline Wozniacki announced that she will retire after the upcoming Australian Open.

The 29-year-old Dane has been battling rheumatoid arthritis for over a year. She was diagnosed after the 2018 US Open, but made the announcement following her elimination from the WTA Finals in Singapore.

"It turns out that I have an autoimmune disease, rheumatoid arthritis, which goes in and attacks your joints," she said. "When the body has a lot of fluids in it and you swell up, you get tired, you get exhausted, all these things.

"In the beginning, it was a shock. You feel like you're the fittest athlete out there. That's what I'm known for, and all of a sudden you have this to work with."

In June, she married former NBA All-Star David Lee at Castiglion del Bosco the Italian region of Tuscany. Twenty-three-time Grand Slam champion Serena Williams was one of her bridesmaids.

Wozniacki, who turned pro in 2005, spent 71 weeks at No. 1—she first reached the top spot in 2010. After trying for years to win a Slam, she finally did it Down Under in 2018, prevailing over Simona Halep in the final to capture her lone major title. She had been a runner-up to Kim Clijsters at the 2009 US Open, and to Williams five years later at Flushing Meadows.

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During the 2014 off-season, she ran an impressive New York City marathon, which saw her complete the the 26.2-mile run.

"This was the toughest physical test I've ever [had]. It's so hard," she said. "You have to keep going, keep going."

Coached by her father, Piotr—a former professional soccer player—she has amassed 30 career singles WTA titles, including the 2017 WTA Finals. A three-time Olympian, Wozniacki was her country's flag bearer at the opening ceremony in Rio de Janeiro.

"With 30 WTA singles titles, a world #1 ranking for 71 weeks, a WTA Finals victory, 3 Olympics, including carrying the flag for my native Denmark, and winning the 2018 Australian Open Grand slam championship, I've accomplished everything I could on the court."

Wozniacki is currently ranked No. 37.