Caroline Wozniacki will become one of the more unlikely year-end world No 1s if she wins two matches at the WTA championships, which start on Tuesday.

Little considered only 18 months ago and from a nation of only five million people, Wozniacki has climbed steadily to a position from which she should earn the 2010 accolade during the women's season-end tournament.

After the 20-year-old Dane first reached the top earlier this month she said: "This is a really big step for me - it doesn't feel like it's real." Her words tempted some critics to suggest that it isn't.

They suggested that the "real" No 1 is Serena Williams, who has been restricted by injury to only 13 tournaments, and that Kim Clijsters, a mum, has played only 14, while super-fit Wozniacki has had the advantage of battling through 23.

Some point out that Wozniacki has yet to capture a Grand Slam title. Instead, she is the third woman in the last two years, after Jelena Jankovic and Dinara Safina, to reach No 1 without winning a major.

Others are unimpressed with Wozniacki's style of play, which has been described as too defensive, though she believes that perception is misleading.

She is in the process of constructing an unflashy, multi-faceted game, enabling her to play in a disruptively complex fashion and to adapt to different opponents and conditions.

Even without the crash-bang-wallop impact of the Williams sisters or other leading players, Wozniacki's style is arguably more sophisticated than she is given credit for.

It is certainly effective, having gained her six titles this year.

And if Wozniacki's game does not inspire awe, her photogenic good looks and outgoing personality have attracted admiration and increased her marketability. These qualities helped attract several sponsorships - Adidas, Babolat, Sony Ericsson, Danske Invest, Europaeiske, and e-boks among them - while her playing ability has brought 12 titles altogether and about $5 million in prize money