The 19-year-old, seeded third at the tournament, slipped behind the baseline while facing former world No. 1 Karolína Plíšková and immediately grabbed her left knee, visibly struggling to continue.
Mboko had lost the first set 6-2 but was mounting a strong response in the second, leading 4-3 and pressing for a break point at deuce when the injury occurred.
“No stability right now” as concern grows on court
Although she managed to get back to her feet without assistance, Mboko quickly signalled discomfort and spoke to the physiotherapist, saying there was “no stability right now.”
She then made her way carefully to her bench, where she sat with a towel over her face before retiring from the match minutes later.
It marked her first singles appearance on grass this season, adding further uncertainty to her immediate form on the surface.
Plíšková acknowledged the unfortunate nature of the result, saying: “I think we played quite a good game today, and I think she was improving as the match was going. I wish her only the best, and of course, this is not the way how we want to win. So hopefully she's going to be fine for Wimbledon.”
Wimbledon hopes now uncertain after early grass setback
The injury casts doubt over Mboko’s participation in the remainder of the short grass-court swing, including the upcoming Wimbledon Championships, which begin in three weeks.
It also raises questions about her scheduled doubles involvement at Queen’s Club alongside tennis icon Serena Williams, who recently returned to competitive tennis after nearly four years away.
The pair had already drawn significant attention after winning their opening match 7-6 (2), 6-2 against Erin Routliffe and Nicole Melichar-Martinez.
They were due to face Leylah Fernandez of Laval, Quebec, and Germany’s Laura Siegemund in the WTA 500 quarterfinals before Mboko’s withdrawal changed the draw.
Strong Canadian doubles run continues despite setback
Elsewhere at the tournament, Canada still had reason for optimism as Ottawa’s Gabriela Dabrowski continued her strong doubles form alongside Brazil’s Luisa Stefani.
The second seeds produced a commanding 6-3, 6-2 victory over Liudmila Samsonova and Miyu Kato, extending a successful run that has included a Strasbourg International title and a semifinal appearance at the French Open.
Dabrowski and Stefani will next face Americans McCartney Kessler and Iva Jovic in Thursday’s quarterfinals as they look to maintain their momentum on grass.
Injury clouds promising Canadian grass-court narrative
Mboko’s abrupt exit adds a somber note to what had been an exciting week for Canadian tennis at Queen’s Club, particularly given her rising profile and the high-profile doubles pairing that had drawn global attention.
Her recovery timeline will now determine whether she can return in time for Wimbledon—or whether her grass season ends before it truly begins.