No wonder she is the world's highest-earning sportswoman. Give Maria Sharapova a spare half an hour away from tennis and she will probably spend it studying the latest sales figures for the clothing ranges she helps to design.
"I love that stuff – I really, really do," Sharapova says, laughing out loud at her obsession with the subject. "I actually just got my selling report for this spring. When things have been on the shelves for a few months you start seeing the sell-through and the value of the product and percentages and stuff. Then you look at the shapes of what worked for the spring and summer, the consumer reports, and you work with that and you build what people look for – what colours they would prefer more in the spring."
Does she ever go into shops and see who is buying what? "I do it all the time," Sharapova says. "I always talk to the manager and duty people to find out what's been doing well. We talk about things. I love getting consumer reports. I think it's one of my favourite things, studying what people have to say about the product and then trying to make it better.
"It's fun for me. Everyone who goes into a store interacts with the manager or the people on duty who help them. When that person goes behind the door and marks everything down you then get a whole report on items, from comfort to style. People talk a lot in the stores. They get their advice and opinions and they never lack that, so it's really beneficial."
When you consider the work that Sharapova has put in on the court and in the gym over the last three years it is a wonder that she has the time or the energy for anything else. After two shoulder operations it seemed she might never recapture the form that took her to No 1 in the world rankings and helped her win three Grand Slam titles, but the 24-year-old Russian will go to Wimbledon next week on the back of her best run of form since she went under the surgeon's knife three summers ago.
Since the appointment of a new coach, the Swede Thomas Hogstedt, at the end of last year, Sharapova has shown steady improvement, culminating in her run to the semi-finals of the French Open earlier this month, her best performance at a Grand Slam event since she won the Australian Open at the start of 2008. She is also back up to No 6 in the world rankings, though she insisted: "I have bigger goals than that."
Even with the return of Serena Williams, Sharapova is the favourite of many to win Wimbledon, where she lifted her first Grand Slam trophy seven years ago. The return of the Williams sisters is the talk of the women's game, though Sharapova is not one for tennis gossip.
"I don't spend a lot of my time in the locker room," she said. "That's my least favourite place in the world. I do my job at the site. I play my matches. I do what I have to do and I prefer to live my life away from the site rather than talk tennis all day."
As she sits in a small Women's Tennis Association office, Sharapova is clearly happier talking about the fashion business. She is the sort to look a million dollars whatever she wears, but with her hair down over her shoulders, wearing a white T-shirt with black leggings, the only clue to her fame and fortune is a large engagement ring on her finger. It was at the end of last year that she revealed her intention to marry Sasha Vujacic, a Slovenian basketball player with the Los Angeles Lakers.
Last summer's most recent Forbes list of the world's highest earning athletes calculated that Sharapova makes $24.5m (£15.1m) a year, more than any other woman. She had a wide range of endorsements and recently signed the biggest individual sponsorship deal in the history of women's sport. The eight-year extension of her agreement with Nike is said to be worth $70m (£43.1m).
As part of the deal Sharapova earns a percentage of sales. She has a collection of Nike sportswear and is the face of Cole Haan, a wholly owned Nike subsidiary which sells clothes, shoes, handbags and accessories.
Nearly all leading sportsmen and women have contracts with clothes manufacturers, but few treat the association as seriously as Sharapova, who takes full advantage of her globe-trotting. "I've been to really cool cities in the last few weeks – Madrid, Rome and Paris – and I love walking around," she said. "I find a lot of inspiration in street style and watching women walk, the way they wear things and what they're wearing. I take a lot of pictures. I do a lot of collages, and that ultimately goes to Cole Haan and Nike."
Sharapova also draws her own designs. "I do sketches but I'm no Picasso or anything. I never really studied it, so I'm not professional. But I am good at bringing ideas to the table. There's a whole team behind with materials and branding and all of that. They help me bring ideas to life. I bring a lot of sketches and I take pictures around the world, whether it's architecture or something with little details.
"It's fun for me. I feel like it's an achievement. Tennis is something I've worked for since I was four years old. It's something that I work for on a daily basis. I didn't study design or go to school for it, so to be appreciated for something, for people to go in a store and like something that I did, having not had so much experience, is really flattering, a surprise. I think people that buy it don't buy it because they see me as a designer, but because they like my style or the way I thought of things."
Seeing people wear her designs brings a particular buzz. "I was just at a club practising," she said. "There was a little junior tournament and I saw two girls wearing a dress of mine from the Australian Open. They were just so adorable. It was over the bottom of their knee, it was so cute. It's really flattering."
Were there times, conversely, when she saw women buying her dresses who might not look so good in them? "No, I've never thought that. Think of the sales!"
With such a head for business it is a safe bet that in years to come Sharapova will not follow the traditional ex-players' path from the court to the commentary box. "I don't see myself locked in a cubicle for hours on end talking cross-courts and down-the-lines," she said. Nevertheless, she does not rule out staying in tennis in some capacity. "No matter what you study, the thing that you know best is what you grew up with," she said.
For the moment, however, there are trophies to be won. Would she prefer to win Wimbledon again or the French Open, which would complete her Grand Slam collection? "I'd win Wimbledon again, absolutely," she said. What is it about Wimbledon that so entrances her? "It's just that feeling that I have when I go on the court there. Having won it helps. I'd love to repeat what I did in 2004. Nothing, obviously, will take your name away from that trophy, but I want it on there again."
She recalled her first visit to the All England Club. "That was the first time I really fell in love with it. I was 15. It was two years before I won. I was runner-up to Vera Dushevina in the junior final. It was a Sunday final. We finished after the men's final so everyone had already left the courts and it was just deserted.
"I was probably one of the last ones to leave and I remember just looking back. There was that big clock and the ivy around the gate and I just felt: 'There's just something so amazing about this place. I want to come back.' Two years later I won it, so it's just crazy how things work out."
Sharapova admitted that 2004, when she won as a 17-year-old, felt a long time ago, but added: "I love the fact that I'm 24, that I have a lot of experience behind my back. I wouldn't change my age for anything." Besides, Wimbledon can have a rejuvenating effect. "Every time I come there I still feel that amazing energy I felt when I was 17."