Pressure on Caroline Wozniacki to prove a worthy number one

The 20-year-old Dane rose to the top of the women's game for the first time earlier this month following a season that has seen her pick up six titles. Wozniacki's ranking has, however, been questioned by some as she is yet to win a grand slam title, while Serena Williams has also been out since Wimbledon after cutting her foot on glass at a restaurant. That injury forced defending champion Williams to pull out of this week's $1.55million round-robin event, while sister Venus - who lost in last year's final - has also withdrawn with a knee complaint.

With the Americans out of the tournament, which starts today, the spotlight has fallen squarely on Wozniacki, who heads an eight-player field that between them has won just four grand slam titles. Veteran Kim Clijsters boasts three of those - the other is French Open champion Francesca Schiavone - and is the only player to have previously won the end-of-season title.

The Belgian won the crown in 2002 and 2003 when it was held in Los Angeles and looms as Wozniacki's biggest rival after her US Open success in September. That victory helped Clijsters qualify for the Doha event for the first time since 2006. "This means a lot to me," she said after qualifying. "This in itself is a goal for me, and a highlight."

While Clijsters may be happy just to have made it to the tournament Doha, she will be one of the favourites to lift the title after being made the third seed and pooled in the opposite group to Wozniacki. Clijsters has been drawn in the White Group with Russian second seed Vera Zvonareva, who she beat in the final at Flushing Meadows, as well as the temperamental east European pair of Serbian Jelena Jankovic and Belarusian Victoria Azarenka, who qualified following Serena Williams' late decision to pull out.

Jankovic cut a forlorn figure at a media conference yesterday, her strained voice and subdued demeanour confirmation that all is not well with the former world No 1. "I'm having some health problems, I have sinus problems," she croaked into the microphone. "I'm still not 100 per cent. I'm not in the form I was in the first half of the season, but that's due to a lot of injuries. I twisted my ankle and had back problems so that also resulted in not good preparation. That has affected my confidence."

Wozniacki heads the Maroon Group that also includes Schiavone, Elena Dementieva and the Australian French Open runner-up Samantha Stosur, who is the only non-European to have qualified. The top two players in each group will qualify for the semi-finals before the final is played on Sunday.