"Further, I think female tennis player brands embody a particular set of qualities, such as strength, power, beauty, success, that some brands find appealing because it enables them to target specific consumer groups, thus strengthening perceptions of their brands -- for which corporations are prepared to pay," he told CNN.

"The fact that some of the recently successful players, such as Li Na, are from growing or strong economies, has been helpful in drawing in new revenue streams to the sport from sponsors and commercial partners that previously may not have had an involvement in tennis."

While Sharapova and the Williams sisters have their own off-court business empires, the WTA actively helps players establish their own brands.

"One of our competitive advantages is that we have so many compelling individual stories," Allaster said.

"Our team is there to help develop their brand plans. Some of them have agents who do that, others don't -- that's where the campaign helps. What's most important is that they be themselves."

The WTA Tour has not always been in such a healthy situation.

When Allaster joined in 2006, having made her name at Tennis Canada as a reviver of struggling tournaments, she faced a situation where players were complaining of burnout.

"We needed radical change. The bottom line was at the top tournaments players weren't consistently showing up, and that was impacting our credibility -- media were talking about it, sponsors were questioning 'are they really going to show?' " she said.

As part of its "Roadmap reform," the WTA cut the number of top-level events players had to enter from 26 to 20. It's now 22, and prize money is up 51%.

"We had grown and grown and grown, there was no shortage of people wanting to do WTA tournaments -- if anyone raised a hand, we said come on. But there's only so many top-10 players," Allaster said.

"The intensity of their play through that period just escalated and their bodies were breaking down. We knew we had a commitment system that couldn't work."

In the 1990s the women's game was invaded by girls in their early teens, such as Martina Hingis and Kournikova, whose stars burned brightly but comparatively briefly.

More recently top players such as Kim Clijsters and Justine Henin retired twice each before they were 30. Both battled with injuries at the end of their careers.

In view of these issues, the WTA's emphasis is now on prolonging the careers of marquee players such as the Williams sisters.

Both have been selective about their playing schedule as they have battled back from injuries and serious illnesses, though Serena has not opted out of the tournament commitment system -- which, under WTA rules, she could do as a top-10 player over the age of 30.

"We've been able to take the average career length from 12 years to now 15 years. I'd rather have 15 years of a superstar than a couple of great years then injured," Allaster said.

"Both Serena and Venus are a gift to women's tennis. Venus is thinking long term and I know Serena is, along with others."

The WTA's pressing business goal is to find a replacement for main sponsor Sony, which concluded an eight-year partnership at the end of 2012.

"We'll get through that. I'd like to have it for 2013 but usually a sales cycle for a global multimillion-dollar sponsorship is 18-24 months, and we are 10 months into this," Allaster said.

And if there is ever any hint of complacency about continuing the WTA's success, Allaster will remind the players of the words of that pioneering nine.

"They're proud of women's tennis and proud of our success. A couple of them looked at me poignantly and said 'Don't let them catch us.' We didn't work this hard for women's tennis not to be No. 1."