World's richest tennis players

Power in the game of tennis is usually measured by the speed of the serve or the force of a player's ground strokes.

By these measures, Andy Roddick would be considered the most powerful tennis player thanks to his world record 155-mile-per-hour serve in last year's Davis Cup and his tour-leading 758 aces this year. On the women's side, Venus Williams holds the record for fastest serve at 128 miles per hour.

Slide show: World's most powerful tennis players

At Forbes.com, we measure power in terms of the money you make and the media exposure you get. From that standpoint, 18-year-old Maria Sharapova is tennis' most powerful player. She's only won one Grand Slam tournament (last year's Wimbledon) compared to seven for Serena Williams.

But the 6-foot 1-inch Russian has secured $15 million in annual endorsement income, and her cover girl good looks make her popular on the Web and with magazine editors.

US Open facts and figures

In putting together our list, we used the methodology from our annual list of the world's most powerful celebrities. We looked at the highest-paid men and women in tennis over the past 12 months. We totaled prize money, appearance fees and endorsement income.

We then looked at their media exposure as measured by Google hits, press clips and TV and radio mentions. Lastly, we took into account appearances on the cover of three tennis magazines: Tennis, Tennis Life and Tennis Week.

Training like a pro

Prize money for our list of ten players was $26 million over the past 12 months, or just 22 per cent of their total income.

The bulk of the income for the top players is from endorsements, with shoe and clothing deals leading the way. The past year has seen unprecedented turnover in these deals for the top players.

Nick Bollettieri: The man behind the Oakleys

Sharapova's deal with Nike surged thanks to her Wimbledon win. Nike has the two top-ranked players in the men's game, Roger Federer and Rafael Nadal, under contract, so, after 17 years, it cut ties with Andre Agassi.

Coolest tennis gear

Reebok dropped its top player, Andy Roddick, who moved onto Lacoste. Venus Williams, who signed a $7 million a year deal with Reebok in 2000, still wears the company's sneakers and clothing -- even though Reebok didn't pick up the option on her contract.

While many top players are losing their deals, Anna Kournikova, who hasn't played a professional match in more than two years, still cashes checks from Adidas.