Two-time Wimbledon champion Petra Kvitova retired from professional tennis Monday after a first-round loss at the US Open.

The 35-year-old Czech, who announced before Wimbledon that New York would be her final tournament, fell 6-1, 6-0 to France's Diane Parry. Kvitova revealed she had contracted COVID-19 three weeks earlier and had struggled with her fitness.

Kvitova won 31 WTA singles titles, including Grand Slam crowns at Wimbledon in 2011 and 2014. She rose as high as No. 2 in the world rankings, posted eight top-10 seasons (2011-15, 2018-20), and earned a bronze medal at the 2016 Rio Olympics.

"I've never been world No. 1, but I think still those two Grand Slam wins is above the world No. 1. So that's how I'm going to take it, especially the Wimbledon ones. I'm proud of many things," said Kvitova.

"Throughout her career, Petra competed with humility and resilience and thrilled tennis audiences with her exciting brand of tennis," Portia Archer, CEO of the WTA, said Monday in a statement.