Women's tennis players have a history of retiring young but Justine Henin, 25, stands alone in doing so as the world's number one player.
It is for that reason that Wednesday's announcement comes as a considerable shock.
True, she has had a pretty average season so far, winning only two titles and suffering heavy defeats by rivals Maria Sharapova (6-4 6-0, Australian Open) and Serena Williams (6-2 6-0, Miami).
She's not cutesie-wootsie but the way she has evolved as a tennis player is unbelievable
But that run came off the back of a quite phenomenal 2007, in which she won two Grand Slams including her third straight French Open title, triumphed at eight other tournaments, and won 63 of 67 matches - a mind-boggling success percentage of 94.
She was the Roger Federer of women's tennis. In December, she was at her peak, beating Sharapova to capture the year-end championships and becoming the first player since 1997 to win 10 titles in a season. She was also the first player in history to win over US$5m in a season.
It was also a remarkable year in Henin's personal life.
In January, she pulled out of the Australian Open for personal reasons, later revealing that she had split from her husband of four years, Pierre-Yves Hardenne. Reports suggested Hardenne felt uncomfortable with his role - or lack of it - within his wife's entourage.
Henin never revealed the reasons behind the split, just as she has never explained why she became estranged from her father and brothers following the death of her mother when she was 12.
But by the French Open last year, the family were reconciled following a near-fatal car accident involving her brother David, and Henin was able to share her historic title win with them.
"It's been a huge step in my life," she said. "I'm glad I gave them this victory because everyone suffered from the situation in the last few years. Finally, we are united in joy, and we can share this moment. I feel so happy."
Henin's backhand is one of the best the game has seen
Henin had long suffered in comparison with her fellow Belgian Kim Clijsters, who was 24 when she retired last year with one Grand Slam title to her name.
Clijsters was bubbly and open, Henin was intensely private. Clijsters was hugely popular among her fellow players, Henin kept herself to herself, preferring the company of her coaching team.
But the sight of Henin sharing an emotional victory with her family cast her in a different light and seemed to change attitudes.
Women's tennis pioneer Billie Jean King was always at a loss as to why Henin did not earn more respect.
"I don't know why we're not talking about Justine Henin all the time because, for her size, she's the greatest athlete we've ever seen.
"I don't know why she's not more appreciated - she's not cutesie-wootsie - but the way she has evolved as a tennis player is unbelievable."
Standing at only 5ft 5ins - with most of her 6ft-plus rivals towering above her - Henin had to work hard to develop a serve which would complement a brutal forehand and a backhand John McEnroe describes as the best the men's or women's game has seen.
She suffered her fair share of injuries, as well as a debilitating illness affecting her immune system which she contracted in 2004 and which continues to affect her from time to time.
The constant battle to stay fit has undoubtedly contributed to her decision to retire. She first picked up a racquet when she was two and turned pro in 1999 when she was 16. This was her 10th year on a tour which has placed increasingly heavy demands on its participants.
Late last year, she told the BBC's Inside Sport programme: "I'm doing this because I love the competition, I love to push my limits, trying to be a better player.
"But my friends aren't on this tour. I'm very focused on myself. I don't think about the other players except that I have a lot of respect for them."
Her announcement on Wednesday - less than two weeks before the start of her favourite Grand Slam where she would have been favourite to win for the fourth year running - leaves more questions than answers.
But following a year in which she completely dominated the women's game and made peace with her family, perhaps Henin - like Clijsters before her - no longer wants to lead the lonely, and often gruelling, life of a tennis pro.
She will be missed - not least for that dazzling backhand.