Amelie Mauresmo withdrew from the Australian Open with a back injury ahead of her quarter-final against unseeded Colombian Fabiola Zuluaga.
Mauresmo had made it to the last eight without dropping a set
The French fourth seed picked up the injury stretching for a backhand volley during her fourth-round match against Alicia Molik.
Mauresmo held a morning practice session on the Rod Laver Arena before leaving the court in tears.
Zuluaga faces Justine Henin-Hardenne or Lindsay Davenport in the semi-finals.
"As you may have seen on the court, I am not able to play my quarter-final
match," said Mauresmo.
"I have pain so I have to withdraw from this tournament. It's a muscle strain on the left side of my back.
"It's not great. It could get worse if I play and the best thing to do is to rest."
Mauresmo, who reached her only Grand Slam final in Australia in 1999, had been in excellent form in the first week of the tournament.
"It was probably a good opportunity for me here in Australia," she said. "I always play well here. That's just the way it is, there is nothing much to do about it.
"I felt I was playing some good tennis and had some opportunities in this tournament so it's a big disappointment.
"I really was hoping that maybe I could handle the situation and handle the shots a little bit better but I realised this morning when I practised that it was not going to be possible."
Zuluaga is the first Colombian to reach the semi-finals of a Grand Slam.
"It feels good to be in the semi, but I didn't want it to be this way the first time," she said. "I'd rather play matches than have the rest."