Former champion Bianca Andreescu has withdrawn from the U.S. Open due to injury, organisers said on Saturday, after the Canadian suffered a stress fracture in her back.
Andreescu, who won the tournament in 2019, lost her opening match at the Citi Open in Washington D.C. last month before going down in straight sets to Camila Giorgi at the Canadian Open.
She appeared to be in discomfort against Italian Giorgi and needed to call a physiotherapist on court.
Andreescu then withdrew from the Cincinnati Masters, saying: "During my match in Washington I started experiencing pain in my back that kept getting worse and I did everything I could the other night in Montreal to play at my highest level.
"All of this led me to undergo medical examinations and sadly the results have revealed a small stress fracture in my back."
Andreescu, 23, was scheduled to face Ukraine's Lesia Tsurenko in the U.S. Open first round.
Former world number two Paula Badosa also said on Saturday that she would miss the year's last Grand Slam with an injury.
The 25-year-old Spaniard, who was due to play Venus Williams in a first-round match under the lights on Tuesday, announced she was shutting down her season to focus on getting healthy.
"Those of you who know me know how much I like to compete and how difficult it has been to make this decision... See you next year, stronger than ever," Badosa said on social media.
It has been a season to forget for Badosa who missed the French Open with a stress fracture in her spine and withdrew from her second-round match at Wimbledon due to a back injury.