London - The imposing figures of Serena and Venus Williams are looming over Wimbledon as the most famous sister act in sport attempts to maintain a decade of dominance at the All England club.
At least one Williams sister has appeared in 10 of the last 11 women's singles finals stretching back to 2000, when Venus downed Lindsay Davenport in straight sets to claim her maiden Grand Slam triumph.
Since then the sisters have turned Wimbledon into a personal fifedom, winning the title on nine occasions -- Serena with four, Venus with five.
But the $2.9 million question -- the record purse on offer to this year's champion -- is the extent to which lengthy injury lay-offs have diminished the power of the all-conquering American duo.
Until her appearance at this week's Eastbourne WTA event, Serena had not played since last year's Wimbledon final, where she swatted aside Russia's Vera Zvonareva in straight sets.
Since that imperious victory, the 29-year-old 13-time grand slam winner has struggled with a life-threatening health problem before suffering a serious foot injury when her foot was sliced open by broken glass.
Serena insists she arrives at Wimbledon merely grateful that she is in the draw, and claims to have put aside thoughts of defending her crown.
"I'm just taking everything one day at a time, and I'm not putting too much expectation on myself or on my game," she said.
The effects of her extended lay-off were plain to see at Eastbourne this week, where she struggled past Tsvetana Pironkova 1-6, 6-3, 6-4 before exiting against Zvonareva in the second round, 6-3, 6-7 (5/7), 5-7.
Elder sister Venus is in a similar position, also returning from injury at Eastbourne this week after a prolonged absence.
The 31-year-old elder Williams sister has hardly played since the Australian Open in January, when she retired after one game of her third round match against Andrea Petkovic after suffering an abdominal injury.
Venus avenged that loss to Petkovic in the first round at Eastbourne before dismantling Ana Ivanovic 6-3, 6-2 to reach the last eight.
While the Williams sisters are far from their respective peaks, it remains to be seen which of the pretenders to their Wimbledon throne are best placed to exploit the potential vulnerability of the Americans.
Denmark's Caroline Wozniacki has the top seeding and the world number one ranking, but with only one grand slam final appearance in her, few are expecting the 20-year-old to break her duck on grass, her least favourite surface.
"My main goal this year is to be a grand slam champion," Wozniacki said. "I want to win one. It would be disastrous if I could not make it happen. I just want to enjoy every time I play on the court."
Much interest will centre around the campaign of China's Li Na, the newly crowned French Open champion who has reached the final of both grand slam tournaments so far this season.
Li's victory at Roland Garros was watched by an estimated 100 million people in her homeland, and she is determined to prove that her performance in Paris was no flash in the pan.
"If I don't do well in Wimbledon, maybe people forget me already. These are tough times, you know," Li said.
With world number two Kim Clijsters withdrawing through injury, a potential dark horse is fifth seed Maria Sharapova, the only woman to record a victory over one of the Williams sisters in a Wimbledon final.
The 24-year-old looked in good form in Paris before losing to Li in the semi-finals, and is confident she can progress far at Wimbledon, where she recored a memorable triumph in 2004.
"I know I can improve in time for Wimbledon," Sharapova said. "The aim is to get better with every year. I've a lot to look forward to."