Henin's fighting qualities made up for her lack of size
Tennis legend Billie-Jean King says the retired Justine Henin should be regarded as the best player in the modern women's game.
Henin won 41 singles titles, including seven Grand Slams, before calling time on her glittering career at the age of just 25 on Wednesday.
"Pound-for-pound, Justine was the best player of her generation," said King.
Serena Williams, one of Henin's main rivals, added: "She was a great champion and gave me so much trouble."
Serena's sister Venus praised Henin's character and refusal to accept defeat.
"She was a great opponent and a real fighter," she said.
"She always challenged herself to play her best tennis, no matter what the circumstances.
"I don't know what the details are but if she made that decision it's probably the best decision for her.
If I was 25 and I'd won so many Grand Slams, I'd quit too
"My prayers are with her and I hope that she continues to lead the life that's best for her."
The WTA confirmed on Friday that Henin will be removed from the next world rankings.
Maria Sharapova, ranked second behind Henin and poised to take over the top spot, said: "She's 25 years old and she's achieved so much in her career.
"If I was 25 and I'd won so many Grand Slams, I'd quit too. Without being the strongest or the biggest, she's won so much.
"She's an inspiration. There's so many things to life and I'm sure she wants to explore them. I definitely don't blame her for retiring."
Henin's coach Carlos Rodriguez said tennis fans would remember the diminutive Belgian for the way she conducted herself as much as for her triumphs on court.
"Technically and tactically she has it all. But I think she will be remembered for the way in which she won and lost and the way she never gave up no matter what was going on in her life," said Rodriguez.
"She never craved fame and money. All she wanted to do was play and win."
King agreed with Rodriguez's assessment of Henin's contribution as an ambassador for the sport.
"I trust she has not come to this decision quickly or easily and I wish her the very best," added King.
"Justine is an extraordinary player, a special person and a true champion in both tennis and in life."
World number three Ana Ivanovic, who lost to Henin in the final of last year's French Open, said the diminutive star brought a style of her own to the sport.
"Tennis loses another champion, she was a great player and she achieved so much," said Ivanovic.
"She brought a lot to the women's game.
"Justine had a completely different game to any other girl on the tour probably. She worked really hard and last year she had some amazing results. I'm sorry to hear this."
Henin is the first woman to walk away from the sport while top of the rankings, while her remarkable 10 titles from 2007 are still fresh in the memory.
But one title which did elude Henin was Wimbledon and the announcement of her retirement came just two weeks before she was due to defend her French Open crown in Paris.
She is a special player because she can play on any surface
Men's world number one Roger Federer
And the men's world number one Roger Federer admitted he was surprised at the timing of the announcement.
"It's obviously a shock for the tennis world," said Federer.
"It's a particular surprise before Roland Garros and Wimbledon, which she's never won.
"It's quite surprising and unfortunate that she's out of the game but she will have her reasons.
"She is a special player because she can play on any surface and it's remarkable that she's won so many tournaments because she is small and the tall players coming in now have an advantage.
"I couldn't imagine deciding out of the blue to retire, especially if I was number one.
"I would prefer to take a year off if it was all getting too much for me, rather than saying straight out that I'm not going to go on."