LONDON - Canada's Victoria Mboko withdrew from her first-round match at the HSBC Championships on Wednesday after sustaining a knee injury during the second set.
Mboko, seeded third at The Queen's Club in West London, slipped behind the baseline and immediately grabbed her left knee while facing former No. 1 Karolina Pliskova of Czechia.
The 19-year-old from Burlington, Ont., lost the first set 6-2 and was up 4-3 in the second and trying to break with Pliskova serving at deuce.
Mboko got up on her own but then told a physiotherapist there was “no stability right now."
She walked gingerly to her bench and put a towel to her face as she sat down. Minutes later, she retired from the match.
It was Mboko's first singles match on grass this season.
"I think we played quite a good game today, and I think she was improving as the match was going," Pliskova said after the match. "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."
The injury puts in doubt Mboko's participation for the rest of the short grass season, including Wimbledon in three weeks, as well as her doubles partnership at Queen's Club with tennis legend Serena Williams.
The 44-year-old Williams made her return to competitive tennis after nearly four years on Tuesday, when she teamed with Mboko for a 7-6 (2), 6-2 win over New Zealand's Erin Routliffe and Nicole Melichar-Martinez of the United States.
Williams and Mboko were scheduled to face Leylah Fernandez of Laval, Que., and Germany's Laura Siegemund in the quarterfinals Thursday at the WTA 500 event.
Earlier, Ottawa's Gabriela Dabrowski and Brazil's Luisa Stefani continued their run of good form with a 6-3, 6-2 win over Russia's Liudmila Samsonova and Japan's Miyu Kato.
Dabrowski and Stefani are coming off a clay season that saw them win the Strasbourg International and advance to the semifinals of the French Open.
The second seeds will face Americans McCartney Kessler and Iva Jovic in Thursday's quarterfinals.
— With files from The Associated Press
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