Fourth seed Venus Williams blocked out the pain of the worst strain she has suffered to win through to the third round of the Australian Open.
The No.4 seed battled back from a groin injury to oust Czech Sandra Zahlavova 6-7 (6-8) 6-0 6-4.
It appeared as though the only American woman left in the tournament was about to depart when Williams broke down in the first set.
She clutched at her right groin after hitting a forehand during the first set tiebreaker against Zahlavova and screamed in pain.
After losing the set 7-6 (8-6) Williams limped off the court to the medical room for an injury time out.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
She returned with her right leg heavily taped and stunned her opponent by racing through the second set without losing a game.
In the third set games went with serve until Williams scored the vital break to lead 4-3 and served out the match 6-4.
"This is probably the most acute one I've had," Williams said.
"In recent times it's been one of the toughest ones for sure but I just wanted to stay on court and survive.
"Obviously I wasn't able to play at my exact level so I had to play smarter and hang tough."
Williams said had she not been playing a grand slam event she would have withdrawn from the match.
She is unsure how the injury will respond to treatment however.
"I don't know. I'm going to try to recover for Friday and get ready to play and bring my best tennis and hopefully I can come through," she said.
Earlier, dual grand slam champion Svetlana Kuznetsova joined former Open winner Justine Henin and world No.1 Caroline Wozniacki in the third round.
Kuznetsova scored a straightforward 6-1 6-4 victory over Holland's Arantxa Rus to advance with little resistance.
Henin and Wozniacki strolled through with effortless wins - the Belgian outclassed Briton Elena Baltacha 6-1 6-3 while Wozniacki humiliated American Vania King 6-1 6-0.
Russian Maria Sharapova, who is fighting back following shoulder surgery, continued her promising form, the 2008 Open champion moving into the third round with a 7-6 (7-3) 6-4 victory over Frenchwoman Virginie Razzano.
Henin, out of the game for two years after retiring, returned at the start of last year and made an immediate impact, reaching the final of both Brisbane and the Australian championships.
Her season was cut short when she suffered an elbow injury during a fourth round loss to compatriot Kim Clijsters at Wimbledon and she did not play for the rest of the year.
Now, though, she says she is refreshed and ready again to re-launch her career, focussing on being at the top for years to come.
"It's not only about Australian Open, it's not only about 2011, it's about a few years that I want to build this second career," Henin said.
"I would say it was very hard last year. I hope this year I'll get the confidence step by step.
"I've been working hard, doing everything I can so I think I'm in the right direction. Even if I have to deal with a lot of things, a lot of things are pretty positive," Henin said.
