Throughout her career, tennis player Anna Kournikova shot to fame as much for her model looks, as on-court success. Clive Brunskill/Getty Images Europe/Getty Images
Legendary tennis coach Nick Bollettieri (far left) started training Kournikova at his Florida Academy when she was just 10 years old.
"When I hear the name 'Anna Kournikova' now, the phrase that springs to my mind is: 'She's my baby,'" said Bollettieri.
"She started the big wave of players from Russia -- don't forget that." Simon Bruty/Getty Images Europe/Getty Images/File
"I've seen them all, but this one actually frightens me," Bollettieri told the New York Times in 1992.
"She knows everything -- what she wants to do and how she's going to get there. She's not only the youngest real prospect I've ever had, but the best. We've had Andre. We've had Courier. We've had Seles, but I can say without hesitation that when I see how this girl can play, at age 10, I'm shocked." Simon Bruty/Getty Images North America/Getty Images/File
Kournikova reached the world No. 1 spot in doubles, yet a singles title always eluded her.
"She was an excellent volleyer, had a very good serve, and could cover her side of the court in a brilliant way," said Bollettieri.
"But when you have to cover the whole court in singles, that lack of weapon, that lack of a killer shot, I think that was probably the reason she didn't win a grand slam in singles." Ezra Shaw/Getty Images North America/Getty Images/File
Kournikova holds the 1995 ITF Junior World Championship trophy, during a dinner at Roland Garros in Paris, in 1996. Clive Brunskill/Getty Images Europe/Getty Images
A baby-faced Kournikova was just 16 when she reached the semifinals at Wimbledon in 1997. She was knocked out of the tournament by her future doubles partner Martina Hingis. FRANK LEONHARDT/AFP/AFP/Getty Images
Kournikova is pictured during the French Open at Roland Garros, Paris.
"I think she did a really good job of balancing being a little girl, growing into a woman, and understanding that there was something special about her looks and her charisma, and how to use that for the betterment of the game," said Ken Merritt, who also coached Kournikova at Bollettieri's famous Florida Academy.
"She changed the women's game of tennis. And I think that in itself makes it a very successful tennis career." Clive Brunskill/Getty Images Europe/Getty Images/File
Kournikova and Hingis won their first grand slam doubles title at the 1999 Australian Open in Melbourne. Clive Brunskill/Getty Images Europe/Getty Images/File
Kournikova blows a kiss to her coach during the first round of the 2000 Australian Open.
"When we were at a major tournament, if Anna Kournikova was practicing, and there was not a big name match on at the stadium, all the guys were there watching Anna Kournikova," said Bollettieri.
"She put the show on, baby. She put the show on." TORSTEN BLACKWOOD/AFP/AFP/Getty Images
Kournikova models Adidas' U.S. Open outfit in Florida. Clive Brunskill/Getty Images Europe/Getty Images
The Russian player recreates Marilyn Monroe's legendary pose during the filming of an Adidas commercial in Los Angeles. Clive Brunskill/Getty Images Europe/Getty Images
Kournikova and Hingis claimed their second major doubles win at the 2002 Australian Open. Sean Garnsworthy/Getty Images AsiaPac/Getty Images
Here, she appears alongside tennis greats Serena Williams and Andre Agassi during a children's tennis event in New York. Theo Wargo/Getty Images North America/Getty Images
Kournikova signs a giant billboard of herself at the Australian Open in 2003.
"I remember back in those days, every magazine cover, every newspaper's back pages, would quite often have photos of her," said PR and marketing consultant for pro-athletes, David Skilling.
"So for tennis, and women's tennis, that was quite an achievement at the time." Nick Laham/Getty Images AsiaPac/Getty Images
Kournikova left the WTA tour in 2003, having become one of the most marketable sportswomen in history.
Here, she models an Adidas outfit during a photoshoot. Clive Brunskill/Getty Images Europe/Getty Images
While she might have left the WTA Tour, Kournikova continued to make appearances at charity events. Here, she poses with pop singer Rihanna at the Arthur Ashe Kids Day in 2005. Bryan Bedder/Getty Images North America/Getty Images
"In terms of sports marketability, there is a limit to how good people look," explained Skilling.
"There had to be a certain level of skill, to warrant brands throwing that kind of money at her."
Here, Kournikova poses at the Adidas Performance Store, in New York. Brad Barket/Getty Images North America/Getty Images
Kournikova competes in the Mercedes-Benz Classic charity event, held in Florida. Al Messerschmidt/Getty Images North America/WireImage
The beautiful tennis player started dating pop singer Enrique Iglesias after appearing in the video for his 2001 single "Escape." Al Bello/Getty Images North America/Getty Images/File
"She's almost like a bit of an enigma," said Skilling. "She came and made such a big impact and was at the front of everything for a long time -- and then retired so early.
"It's almost like, 'was she really there?' 'What happened to this girl?' It wasn't like it was a long period of time where she slowed down gradually.
"So I think that creates a kind of mystique around her."
Here, Kournikova appears at a BAFTA awards evening in 2011. Kevork Djansezian/Getty Images North America/Getty Images