"The Miracle" Zhang Ning has overcome a lot in her long career. She has shaken off doubts and injuries that have nearly derailed her, hit the bottom and climbed back to the top.

All the struggle and the joy will come to a fitting end today when the 33-year-old plays in what will likely be her last match, a gold-medal contest against teammate and world No 1 Xie Xingfang to defend the title she won in Athens. If she wins she will become the oldest woman ever to win an Olympic badminton women's singles gold.

"I am already a miracle," said a tearful Zhang after a nail-biting win over Indonesia's Maria Kristin Yulianti Friday. "I just see it as my opportunity to make new history and make new miracles."

Zhang Ning of China celebrates after defeating Maria Kristin Yulianti of Indonesia in the women's singles semi-final badminton match of the 2008 Beijing Olympic Games, at the Beijing University of Technology Gymnasium in Beijing, on August 15, 2008. Zhang won the match 21-15, 21-15. [Agencies]

Most of her national teammates of the past retired before the Athens Games, but she pushed on, and seemed to get stronger as she got older. This led to Chinese badminton head coach Li Yongbo dubbing her "The Miracle".

Zhang, a soldier's daughter from Liaoning, has trained with the national team since 1991, an era that spawned the last generation of Chinese badminton stars like Gong Zhichao and world champion Ye Zhaoying.

Those were not good years for Zhang, who had a rough start to her career. The low point of her career came during the 1994 Uber Cup final against the host Indonesia.

China was aiming for a historic sixth consecutive Uber Cup title, but the home team was going to be China's toughest challenge. The two teams were tied 2-2 before then 19-year-old Zhang walked onto the court. But Zhang lost to 15-year-old Mia Audina-Tjiptawan in three games, ending China's shot at a title. Zhang has been haunted by that match ever since.

"I can't remember how I lost that match. It may seem absurd, but I pretty much finished that match with my mind almost blank," Zhang recalled.

"Now I realize why my coach often told me I was single-minded back then. It's because I never knew how to cope with different rivals," she said.

She did not attend either the Atlanta or the Sydney Games, and won her first major world title at the age of 28.

When she got to Athens, she was not considered a gold-medal hopeful even though she was the No 2-ranked singles player in China. But after her world No 1 teammate Gong Ruina was knocked out, Zhang got the chance to avenge her defeat in Jakarta, beating Mia Audina-Tjiptawan in an epic three-game battle to become the oldest woman to win an Olympic badminton women's singles title. At that moment, her reputation changed, and "Zhang Ning" became a household name.

Zhang considered retiring from badminton after her Athens success, but found she was still able to compete among the world's elite. A knee injury she sustained a year before the Beijing Games threatened her chances of earning the necessary berth. But just like she has throughout her career, she pushed on, knowing her team would need her experience if it was to perform well on home turf.

"People around me know that I am a very responsible person. If the team and the fans need me, I will do my very best to accomplish my mission," Zhang said Friday.

In her four matches so far in Beijing, Zhang has been precise and determined, striking fear into her opponents.

"I've played each match as if it were my last," she said after beating Thailand's Salakjit Ponsana in her first match.