Jayne Kamin-Oncea-USA TODAY Sports

Former World No. 9 CoCo Vandeweghe is retiring after this week's San Diego Open.

The longtime San Diego-area resident is scheduled for a Thursday quarterfinals doubles match with partner Danielle Collins. The pair play Ukraine's Lyudmyla Kichenok and Latvia's Jelena Ostapenko.

Vandeweghe, 31, reached the semifinals of both the Australian and U.S. Opens in 2017 and won the 2018 U.S. doubles crown with partner Ashleigh Barty of Australia. She also was a two-time quarterfinalist at Wimbledon (2015, 2017).

But Vandeweghe sustained a serious ankle injury in 2018 and was unable to capture her previous form.

"Tennis is tough with everything. It's never-ending, it doesn't stop," Vandeweghe said. "It was very tough to move and ask my body to do what it needed to do. And I couldn't do it consistently. I was able to make inroads, but I was never quite the same.

"Father Time -- or is it Mother Nature -- is undefeated."

Vandeweghe went 341-287 as a singles players. She won six WTA titles (two singles, four doubles). Vandeweghe earned over $8 million in prize money.

Vandeweghe is the niece of former UCLA and NBA star Kiki VanDeWeghe.

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