Four-time Grand Slam champion Naomi Osaka and world No 3 Jessica Pegula have pulled out of the new women's tournament at Queen's Club.
Pegula, the runner-up at last year's US Open, was set to be the highest-ranked player at the WTA 500 event, but the American withdrew alongside Japanese star Osaka on Thursday.
The Wimbledon warm-up event starts on Monday, with female players returning to Queen's for the first time in 52 years.
Pegula lost in the French Open fourth round to wild card Lois Boisson earlier this week and on Wednesday posted images on her Instagram page of the social media abuse she has suffered since the shock loss.
Osaka, who has won both the Australian Open and US Open twice, received a wild card from Queen's organisers.
But she expressed frustration with her form last week after enduring a dismal French Open exit against Paula Badosa.
Queen's Club officials confirmed the withdrawals of the pair on the tournament's official X account.
The absence of two high-profile stars is a blow to Queen's organisers after they added a week of women's action to a tournament that had only featured men since 1973.
The ATP event at Queen's now takes place a week after the women's tournament in west London.
Former Wimbledon winners Elena Rybakina and Petra Kvitova, who has recently returned from maternity leave, are scheduled to feature alongside reigning All England Club champion Barbora Krejcikova in the WTA tournament.
Top-10 trio Madison Keys, who won the Australian Open in January, Emma Navarro and Zheng Qinwen are also in the women's draw.