Stick her next to Venus or Serena Williams and it would seem inevitable that the petite Belgian would have no chance of beating the American sisters. Yet, if Henin is diminutive in stature, she has stacks of other qualities: inner strength, boundless commitment, a ferocious work ethic and technical expertise. And you do not win seven grand slam titles and become the world's No.1 player by accident.
Henin was at the Westburn Indoor Tennis Centre in Aberdeen yesterday, lending her myriad gifts to 16 of the north-east's best tennis talents. She was not inclined to scream at her charges, nor indulge in any hairdryer-style haranguing when they fluffed a volley or lob, but, quietly, insistently, persuasively, she imparted shafts of wisdom here, and doled out slivers of advice there. In common with her fictional compatriot, Hercule Poirot, it was immediately obvious she is button-bright and blessed with plenty of little grey cells.
In which light, one should not be surprised that, aged just 31, she has established her own academy and thrown herself whole heartedly into backing a charitable foundation for sick children in her homeland. Tennis was never the be-all and end-all in her life and her conversation was mercifully free of banalities.
Instead, Henin stressed the need for small nations, such as her own and Scotland, to create more indoor facilities and do their utmost to spread the game's appeal, regardless of the initial costs of these amenities. She added that not everybody can become a champion, but, as Andy Murray had demonstrated, there is no logical reason why countries with no previous tradition of unearthing grand slam winners cannot climb into the spotlight.
"Andy has been a great inspiration, because he has done things his own way, and grown up, both as a player and a person, and risen above the pressure which was heaped on him," said Henin, who triumphed four times at Roland Garros, twice at Flushing Meadow and once at Melbourne Park, as well as collecting Olympic gold in Athens in 2004 and reaching the final at Wimbledon on two occasions.
"Andy is smart, he respects the game and his opponents. He was thrown in against some of the greatest performers [such as Roger Federer and Rafael Nadal], but has come through in brilliant fashion and I have no doubt that he can go on and win many other major tournaments in the future.
"The thing is that he left Scotland and went to Spain to learn how to make himself a better player. I did the same thing when I travelled to the United States [and joined forces with her long-time mentor, Carlos Rodriguez] and I learned so much from doing that, which I was able to put back into the game. I don't think you can start from the viewpoint: 'How do we find the next Andy Murray?' It has to be about the bigger picture, laying the foundations with good facilities, good coaches, and building a system where youngsters want to play tennis because they enjoy it. That happened with me and Kim [Clijsters] when we were both winning titles and people were asking how Belgium had turned into a big tennis country. The main thing is to get it right at the grassroots."
Henin gave birth to her daughter, Lalie, in March, and laughed off the suggestion that she might have retired too early, citing her exertions with her academy, and her duties as a UNICEF ambassador, as the sort of activities she wants to focus on in the future. During her career, she gained fulsome tributes from such luminaries as Andre Agassi ("Justine is one of the most talented women ever to have played tennis") and Billie Jean King ("Justine is the best women's athlete I have ever seen"), but Henin exited the WTA Tour with ambitions which extended beyond simply cashing in on any seniors circuit. She earned $20m with her racket. Now, she aims to invest it in projects she genuinely cares about, and do whatever she can to persuade youngsters of the benefits of healthy exercise.
"You go to Australia and everybody is involved in sport and is part of a club network, and you soon realise how that can help people stay fit. In Belgium, it is a part of our lives, but it is not that important, and I like to think I can change that attitude a bit," said Henin, who might only be 5ft 5in, but is a giant in her home country.
"At the moment, everybody back home is talking about football and looking forward to the World Cup [next summer in Brazil], and it's terrific when you can get your nation excited about sport. I saw that when Andy won at the Olympics and at Wimbledon. But you shouldn't rest on one or two people being successful, you should use what they have achieved to lift others.
"That is why it is so much fun to be here in Aberdeen. I have spoken to the kids and passed on some tips, and they have worked really hard, and will be tired tonight. Not all of them are going to develop into grand slam champions, of course they're not, but if they become more confident, feel better about themselves, improve their skills and learn to work with and respect the others in the group, that is a success story in itself."
She may have retired from tennis, but she is still at the top of her game.