(CNN) -- You don't get any prizes for guessing that Maria Sharapova is the highest-earning female athlete in the world.
But who is the second richest? Is it Serena Williams, the American 13-time grand slam winner? Or is it Victoria Azarenka, the world No. 1 and winner of 35 of her 38 matches this year? And away from tennis, there is Danica Patrick, the only woman to win an IndyCar race and a big drawcard for motorsport sponsors.
In fact, it is Li Na, the world No. 7 women's tennis player and winner of a single grand slam title in a 13-year career.
But that surprise victory at the French Open almost a year ago transformed Li into one of the world's most marketable athletes.
According to Forbes.com, she earned $18 million to April 2012 (up $10 million from 2011) -- $8 million shy of Sharapova's total but $5 million more than third-placed Williams.
So why are brands scrambling to associate with Li, who will defend her title at Roland Garros when the clay-court major starts on Sunday.
"Two words: She's Chinese," says Simon Chadwick, Professor of Sport Business Strategy and Marketing at Coventry University Business School in Britain.
"Li Na is out there on her own, firstly in terms of being a female Chinese sportsperson and secondly in terms of her international profile and success."
The fact that Li plays tennis -- a traditionally middle-class sport -- is also in her favor.
"China has now become the biggest market for luxury brands in the world and there is this kind of convergence between luxury brands and tennis," Chadwick told CNN.
"The kind of people who are interested in those brands are also interested in tennis, so Li Na is a very convenient way of aligning the two."
Li's agent Max Eisenbud, who also represents Sharapova, spotted the potential in 2009 when he signed her to IMG's books.
He concedes that although he thought she had top-five potential, he didn't necessarily expect her to be a grand slam winner.
But at age 29, and in her 20th major tournament, Li beat Francesca Schiavone to become the first Chinese player to win a grand slam singles title and set off a chain of events that had Eisenbud working overnight from a makeshift office to stay in touch with his colleagues in Beijing while the offers flooded in.
"She's basically the Billie Jean King of China," Eisenbud told CNN. "She broke down so many barriers.
"She was the first -- and it's weird that you can say that in 2012 -- that there's somewhere in the world that they just don't have a rich tradition of sports heroes.
"I think that was very cool to see: that the win was a lot bigger than tennis."
Li has signed seven new sponsorship deals since her Roland Garros triumph. Among them are luxury car maker Mercedes Benz and Chinese insurance company Taikang Life Insurance Co.
Eisenbud even managed to negotiate a special deal with Nike to allow Li to wear patches on her clothing -- something not usually permitted by the American sportswear giant.
"I think we did a good job on a hybrid of global brands that could potentially use Li Na to help get a footing in China and then we also wanted to associate with some great Chinese brands," he said.
Eisenbud estimates they could have signed up to seven more deals, but with his experience of managing Sharapova's money-making potential after her 2004 Wimbledon win, he was wary of compromising Li's tennis career.
Li won only six more matches in 2011 after the French Open final, going out in the second round at Wimbledon and the first hurdle at the U.S. Open.
She has been more like her old self in 2012, reaching two finals, most recently at the Italian Open where she lost out to Sharapova over three sets.
"I liked the way I hit on court," she said afterwards. "A lot of positive things and I think I am ready for the French Open."
The reality is that financially at least, it really doesn't matter how Li performs at Roland Garros this time around. She was already nearing the end of her career when she won the title and the deals were negotiated with that in mind.
What IMG and Li's team has done is what Chadwick calls "short-term harvesting."
"It's to make as much money as possible in the period of time they've got left before she retires," said the academic.
"The French Open was all she needed because we're still talking about it now, that's proof that's all she needed."
Which begs the question: would any Chinese player have had the same earning potential as Li had they become the first major winner from the world's most populous country?
Maybe not. Chadwick says Li's added value comes from the fact that she rejected the Chinese state-run sports system, while Eisenbud describes as her "little bit of rebel."
That little bit of rebelliousness is most visible in the red rose tattoo she sports on her chest.
"In Western terms, marketers talk about brand personality," Chadwick said. "And she does have some personality to her, the whole thing about her tattoo, the crazy things she says about her husband (who Li has publicly berated for his snoring)."
"Effectively what Li Na does is give these Western brands a direct route into the Chinese marketplace, which is a notoriously difficult and complex country to do business in."
Li joked in August last year that she still used her husband Jian Shang's credit card when she went shopping because she liked to save money. If Jian ever needs a loan to pay off the bill, he need look no further than his multimillionaire wife.