Canada's Bianca Andreescu will not defend her title at the BNP Paribas Open because of a lingering left knee injury.

The reigning U.S. Open champion dropped out of the WTA Tour Premier Mandatory event on Saturday, four days before the main draw begins.

Andreescu hasn't played a competitive match since she suffered the injury in late October at the WTA Finals in China.

The 19-year-old native of Mississauga, Ont., not revealed the exact nature of the injury.

"As many of you know, I've been working through an injury I suffered last year during the WTA Finals," Andreescu said in a statement released on the tournament's Twitter feed. "It's been a long road to recovery and while I was looking forward to getting back on court and defending my title at Indian Wells, unfortunately I'm still not 100 per cent.

"I would like to thank you all for your continued support and sticking with me on this journey, your kind words have been so uplifting. While I am disappointed that I am not competing next week in a tournament where I have such great memories, I am focused on my recovery and rehab and working hard to get back on the court as soon as possible."

“As many of you know, I’ve been working through an injury I suffered last year during the WTA Finals. It’s been a long road to recovery and while I was looking forward to getting back on court and defending my title at Indian Wells, unfortunately I’m still not 100%."<a href="https://twitter.com/hashtag/BNPPO20?src=hash&ref_src=twsrc%5Etfw">#BNPPO20</a> <a href="https://t.co/XFyKwG5z2o">pic.twitter.com/XFyKwG5z2o</a> —@BNPPARIBASOPEN

"I would like to thank you all for your<br>continued support and sticking with me on this journey, your kind words have been so uplifting. While I am disappointed that I am not competing next week in a tournament where I have such great memories, I am focused on my recovery..." —@BNPPARIBASOPEN

The BNP Paribas Open title last year was the first of three for Andreescu last year after she started 2019 outside the top 150.

Given a wild-card entry to the Indian Wells event — which is the second highest level on tour, behind Grand Slams — after a promising start to the campaign, Andreescu beat Angelique Kerber of Germany in a dramatic final.

Andreescu retired from the next tournament with a shoulder injury that kept her out for months, but then returned in August to win the Rogers Cup in Toronto and the season's final Grand Slam — the U.S. Open in New York.

Despite the absence from play, Andreescu has reached a Canadian record No. 4 in the world rankings.

Denis Shapovalov of Richmond Hill, Ont., Felix Auger-Aliassime of Montreal, Milos Raonic of Thornhill, Ont., and Vasek Pospisil of Vancouver are entered in the men's main draw at Indian Wells. Leylah Annie Fernandez of Laval, Que., has been given a wild-card entry into the women's draw after reaching her first final last week at the Mexican Open.