The Russian 21-year-old is one of the most recognizable and photographed stars in tennis thanks to her blonde looks and figure-hugging outfits.

Sponsorship deals with Adidas, Omega watches, Yonex tennis equipment and Berlei lingerie have made Kournikova one of the wealthiest players on the women’s circuit with career earnings totaling more than US$40 million.

But the vital statistics of Kournikova’s career tell another story.

On Monday Kournikova crashed to her fourth first round defeat in Grand Slam competition this season, losing 6-3, 6-0 to 17-year-old Indonesian Angelique Widjaja.

Since making her debut on the WTA Tour in 1995, Kournikova has failed to win a singles title. She is currently ranked 37th in the world, having previously climbed as high as eighth.

Of the US$10.6 million that dropped into her bank account last season just US$334,000 was earned on court.

Now, Adidas, which reportedly pays US$2.4m a year to be associated with the Moscow-born star, is rumored to be unhappy with Kournikova’s form.

Phil Holland, news correspondent with sports business experts Sportcal.com, believes the game could soon be up for Kournikova as a marketable asset.

“What you have to bear in mind us that sponsors have paid a lot of money to endorse her and the idea is that she produces something in return,” he told CNNSI.com.

“Grand Slams are where they want to see their stars. They don't want to be associated with over-paid stars who are earning top cash but not performing.”

Kournikova has been accused of allowing her off-court commitments to become a distraction and at Wimbledon in June her image suffered a further blow when she lost her temper in an interview with a BBC reporter who suggested she needed to re-focus on her game.

“She’s going on TV but not for the right reasons,” says Holland.“The interview at Wimbledon was uncomfortable for all concerned. If you’re a sponsor you want her to be successful.”

At 21, it may be too soon to say that Kournikova’s best tennis is behind her, but after six years on the circuit the Russian is more the fading veteran than the rising starlet.

Meanwhile there are plenty of upcoming players -- such as Austria’s Barbara Schett, Slovakia’s Daniela Hantuchova and American Ashley Harkleroad – with aspirations to usurp Kournikova as the glamor girl of women’s tennis while adding winning results to the equation.

Ironically, Holland believes Kournikova’s financial success could limit the earnings potential of the young stars coming through behind her.

“Somebody like Justine Henin is playing good tennis but in terms of marketability she's not quite up there,” he says.

“On the other hand somebody like Barbara Schett is getting a lot of attention for her looks but if her tennis is of the same standard as Kournikova's -- although it’s probably better -- she's not going to get the same amount of attention.

“Nobody is going to jump into deals with tennis players simply because of their looks. It's case of once-bitten, twice shy.”

As for Kournikova’s tennis career, a period away from the spotlight could be the key to getting her game back on track.

“If she wants to perform she needs to re-consider what she wants to achieve,” says Holland.

“That might mean stepping down to lesser tournaments, getting back to basics and thinking about a change of coach. It worked very effectively for Andre Agassi a few years ago.”