Wimbledon champion Venus Williams pulled out of the China Open with a left knee injury on Friday, dealing a new blow to tournament organisers.
"It's a new injury that came last night," Williams told reporters. "I'm not fit enough to play a tennis match. It's a pity I can't play but I hope I can play in Guangzhou. Maybe now I can see the Forbidden City."
Williams's withdrawal has left the $585,000 tournament without three of its top four seeds.
Lindsay Davenport pulled out after winning in Bali at the weekend and Venus's younger sister Serena suffered a shock 6-2 7-6 defeat by China's Sun Tiantian in her opening match.
Only world number one Maria Sharapova is left in.
Third seed Venus took a knee-injury timeout late in her 6-3 6-1 win over Spain's Nuria Llagostera Vives on Thursday but had shown no ill effects in finishing off the second round match.
The former world number one has been troubled by knee and various other injuries throughout her career.
Venus, who was due to play Poland's Marta Domachowska in a quarter-final on Friday, is scheduled to appear in Guangzhou, southern China, next week.