LOS ANGELES • Women's tennis world No. 1 Serena Williams has pulled out of upcoming WTA tournaments in California and Miami because of a knee injury, the organisers said on Tuesday.
A statement issued by BNP Paribas Open organisers in California quoted her as saying that she was withdrawing because of a problem with her left knee.
"Sadly, I have to withdraw from the BNP Paribas Open in Indian Wells and the Miami Open," the 35-year-old star said.
"I have not been able to train due to my knees and am disappointed I cannot be there.
"I will keep moving forward and continue to be positive. I look forward to being back as soon as I can."
The world No. 1 ranking will change hands after the Indian Wells event, with Germany's Angelique Kerber set to ascend to the summit once more, owing to Serena Williams' withdrawal.
Organisers of this week's event in Indian Wells, which gets under way today, said a revised draw would be issued later.
Williams' withdrawal means Germany's world No. 2 Angelique Kerber will take over the world No. 1 ranking at the conclusion of the tournament on March 19, regardless of the results due to the finalist points Williams will surrender.
Last year, the American made it to the final at the Palm Springs tournament before a straight-sets loss to Victoria Azarenka.
Williams is a two-time champion at Indian Wells, having won it in 1999 and 2001. However, she went 14 years without entering the tournament after experiencing an episode of racial abuse, but decided to end her boycott in 2015.
She has also not played since defeating sister Venus, 36, in the final of the Australian Open in January to clinch a record 23rd Grand Slam singles title.
She has long been a staple at the Miami Open, winning the tournament a record eight times, with her most recent victory coming in 2015.
This year's tournament runs from March 21 to April 2.
AGENCE FRANCE-PRESSE, REUTERS