Fourth seeded Agnieszka Radwanska pulled out of the Cincinnati Masters tournament on Thursday to attend the funeral of her grandfather in her native Poland.
"Unfortunately, my grandad passed away last Sunday, the funeral is Saturday and I need to be there," Radwanska said. I'm disappointed not to continue with the tournament especially due to my form this week."
Radwanska was scheduled to play a quarter-final match against defending champion Li Na of China on Friday.
Li now advances directly to the semi-finals where she will face an undetermined opponent on Saturday.
On Thursday, Radwanska won her third-round contest over Elena Vesnina 6-0, 6-2 while Li beat German Angelique Kerber 6-4, 6-4.
Radwanska's father is her former tennis coach and her younger sister, Urszula, is also a professional tennis player.
"It was a difficult decision but I need to go home and be with my family," Agnieszka said.