Kim Clijsters rules herself out of Wimbledon with injury

The Belgian, a semi-finalist in 2003 and 2006, had been seeded second for this year's championships.

Clijsters' withdrawal has meant a step up a rung for every seed below the No 1, Caroline Wozniacki of Denmark. Defending champion Serena Williams, now seventh, and her sister Venus, No 23, are the only beneficiaries of the deliberations of the seedings committee, who can choose to promote players well above their current world rankings, unlike in the men's event.

The fact the American siblings have hardly played over the past year has made this year's event look wide open, and an on-form Clijsters would have been as good a bet as anyone to take the title, making the recurrence of a foot injury at the Unicef Open particularly annoying for her.

"I'm very, very disappointed to have to withdraw from Wimbledon after injuring my foot again at the tournament in 's-Hertogenbosch," she said.

"At this moment I feel frustrated that it has to happen now before one of my favourite tournaments," said the 28-year-old, who retired from tennis in 2007 to give birth to her daughter before returning and winning the US Open two years later

"I've always enjoyed being a part of the Wimbledon atmosphere, but I have no other choice now but to rest, recover and to not play tennis for a few weeks."

Apart from Venus and Serena, No 5 seed Maria Sharapova is the only other former Wimbledon singles champion in the field – although ex-world No 1 Jelena Jankovic, the 15th seed, did win the mixed doubles with Scotland's Jamie Murray four years ago.

Jankovic's Serbian compatriot Ana Ivanovic, another former world No 1, has a French Open title to her name, but she will be less fancied to be a contender on grass than the last two winners at Roland Garros, current champion Na Li, seeded third, and 2010 winner Francesca Schiavone, the No 6 seed. Former Wimbledon finalist Marion Bartoli is ninth seed this year.

"The seeding order follows the WTA ranking list, except where in the opinion of the committee, a change is necessary to produce a balanced draw," a statement from the Wimbledon referees' office explained. "The only changes this year are Serena Williams and Venus Williams. This reflects the balance between their proven records and also their lack of competitive play in the past 12 months."

Venus, who has five Wimbledon titles and two US Open crowns to her name, has been a low-ranking seed before, and her 23rd seeding this time means she could meet her younger sister at an early stage this year. She lost in the quarter-finals last year to Bulgaria's Tsvetana Pironkova, who has crept into the seedings at No 32 following the rejig caused by Clijsters' withdrawal.

Serena is the defending champion, having beaten Vera Zvonareva in straight sets in last year's final, but her defeat by the Russian yesterday at Eastbourne suggests she could well struggle to get that far this year.