A back injury forced Urszula Radwanska to retire from her second round match against Melinda Czink, with the Hungarian leading 4-2 in the first set.
The disappointed Polish qualifier said four tough matches before today took their toll on her.
“I was playing very well here and I love this tournament so I’m very disappointed,” she said.
Radwanska said she felt a twinge in her back during Monday’s two-hour, first round epic against the sixth seeded Aleksandra Wozniak.
Radwanska, ranked 126, came from a set down and saved seven match points in the second set to take the match against world No.33 Wozniak.
Radwanska has an appointment with the tournament doctor later today.
Radwanska and her sibling, world No.10 Agnieszka Radwanska – who won in Sydney today – are shaping as tennis’s latest sister act.
They are teamed to play doubles at the Australian Open but Urszula must qualify for the Grand Slam’s singles main draw.