Saint Petersburg: Top seed Simona Halep pulled out of the St Petersburg Trophy yesterday because of a persistent knee injury, propelling a Russian wildcard into the semi-finals.
"I'm really disappointed that I had to withdraw from the quarter-final today, but my knee is not okay," the Romanian Halep, ranked fourth in the world, said.
"After my last match I felt pain and I feel it's risky to continue here."
Halep, who enjoyed an opening-round bye, beat Croatia's Ana Konjuh in the second round in St Petersburg.
Halep's withdrawal saw Russia's 19-year-old wildcard Natalia Vikhlyantseva advance to the semi-finals of the event, where she will meet either defending champion Roberta Vinci of Italy or France's Kristina Mladenovic.
