The 27-year-old British star pulled out of the tournament just hours before he was due to take on fourth-seed Jan-Michael Gambill in the second round.

Rusedski said he hurt his lower left back early in his straight-sets victory over Taylor Dent on Tuesday night, and did not want to chance further injury.

The injury improved on Thursday, but there was still some tenderness and after consulting with his entourage of doctors, trainers and therapists, Rusedski thought the better of it.

"In the past I've tried to battle through things and it's brought me trouble."

Rusedski's match on Tuesday was played in swirling winds and cool temperatures, something he said might have contributed to the injury.

"These things can happen when you get that sort of weather when it's really, really cold. It's really unlucky," he said.

Lapenti out

Meanwhile, Nicolas Lapentti exited in a more conventional manner as the Ecuadorean was beaten by Belgium's Xavier Malisse 6-3 6-4 in their second-round match.

Lapentti fell in just 74 minutes. He broke Malisse in the first game of the opening set but it was downhill fast from there as Malisse broke right back to tie it 1-1 and again to lead 3-1.

Malisse, 20, advanced to the quarter-finals just a week after making the semi-finals in San Jose.

He was joined by American Chris Woodruff, who had little trouble in dispatching German Marc-Kevin Goellner 6-2 6-3. Woodruff will face Gambill in the quarter-finals.