Venus Williams suffered a fresh injury blow on Friday when she was forced to pull out of the Pan Pacific Open with a leg problem before her quarter-final with fellow American Chanda Rubin.

The former world number one, who was playing only her second tournament after being sidelined for six months with an abdominal injury, complained of a pain below her right knee during a practice session just hours before the match.

"I guess, basically, I originally had the issue in Australia," said a dejected Williams, upset in the third round of the Australian Open last month on her return from injury.

"Today, it was very difficult for me in practice to move or play in any way, shape or form that was normal for me. I was getting various treatments from the tournament doctor but at this juncture things just didn't click for me."

Williams was beaten by compatriot Lisa Raymond in Melbourne in her third match since losing to younger sister Serena in last year's Wimbledon final.

"It (the injury) came during Australia. It worked all right to get it better and to keep playing matches there but I was also hindered in Australia, hence my performance," shrugged Venus.

"It's the lower right leg, below the knee and basically it's hard to move, to sum it up. It's not really funny. But good things come to those who work hard and I will."

Top seed Venus added that she had felt a twinge during her only match in Tokyo, a 6-3, 6-4 victory over Japan's Saori Obata on Thursday.

"I'm having a problem with my leg and really can't play today," a tearful Venus told the crowd in Tokyo after hobbling on to court to explain why she could not face Rubin.

"I've done everything I can do at this point. I really wish things could be different but they can't, so I'm just going to deal with the circumstances."

Fifth seed Rubin advanced to the semi-finals of the $1.3 million event, where she faces Bulgaria's Magdalena Maleeva who crushed home favourite Ai Sugiyama 6-1, 6-1 earlier on Friday.