Rusedski finds himself up against world number two Marcelo Rios after Agassi pulled out of the event because of a back problem, which forced him to retire during the first set of his opening round robin match against Alex Corretja.

It is an ironic turn of events after Rusedski was forced to pull out of last year's tournament due to injury after losing his firtst two matches.

It is possible for him to qualify for the semi-finals, but he will have to beat both Rios and fellow Briton Tim Henman to do it.

Henman: Won his opening match

Rios also complained about a sore back following his 7-5 6-1 defeat by Henman on Tuesday, but says he is fit enough to carry on.

Henman can qualify for the last four if he beats Corretja today but lost 7-5 6-3 at last year's Paris Indoor Open - the only previous meeting between them.

"Tim was a good player then, but a better one now so he's going to be tough. But I've also improved, so it should be a very close match," the Spaniard said.

Henman and Rusedski will meet on Friday and defeat for Henman could result in him losing his status as British number one.

Thursday's schedule (play starts 1.00pm GMT):

White Group: A Corretja (Spain) v T Henman (GB), M Rios (Chile) v G Rusedski (GB)